Document Format (PDF) is a file format developed in the
1990s to present documents, including text formatting and images, in a
manner independent of application software, hardware, and operating
systems. Based on the
PostScript language, each PDF file
encapsulates a complete description of a fixed-layout flat document,
including the text, fonts, vector graphics, raster images and other
information needed to display it. PDF was standardized as an open
ISO 32000, in 2008, and does not require any royalties for its
Today, PDF files may contain a variety of content besides flat text
and graphics including logical structuring elements, interactive
elements such as annotations and form-fields, layers, rich media
(including video content) and three dimensional objects using
PRC, and various other data formats. The PDF
specification also provides for encryption and digital signatures,
file attachments and metadata to enable workflows requiring these
1 History and standardization
2 Technical foundations
3 Technical overview
3.2 Imaging model
3.2.1 Vector graphics
3.2.2 Raster images
22.214.171.124 Standard Type 1 Fonts (Standard 14 Fonts)
3.3 Interactive elements
126.96.36.199 Forms Data Format (FDF)
XML Forms Data Format (XFDF)
XML Forms Architecture (XFA)
3.4 Logical structure and accessibility
3.5 Optional Content Groups (layers)
3.6 Security and signatures
3.6.1 Usage rights
3.9 Usage restrictions and monitoring
3.10 Default display settings
4 Intellectual property
5 Technical issues
5.2 Viruses and exploits
8 See also
10 Further reading
11 External links
History and standardization
Main article: History of the Portable
Document Format (PDF)
Adobe Systems made the PDF specification available free of charge in
1993. In the early years PDF was popular mainly in desktop publishing
workflows, and competed with a variety of formats such as DjVu, Envoy,
Common Ground Digital Paper, Farallon Replica and even Adobe's own
PDF was a proprietary format controlled by Adobe until it was released
as an open standard on July 1, 2008, and published by the
International Organization for Standardization
International Organization for Standardization as ISO
32000-1:2008, at which time control of the specification passed
ISO Committee of volunteer industry experts. In 2008, Adobe
published a Public Patent License to
ISO 32000-1 granting royalty-free
rights for all patents owned by Adobe that are necessary to make, use,
sell, and distribute PDF compliant implementations.
PDF 1.7, the sixth edition of the PDF specification that became ISO
32000-1, includes some proprietary technologies defined only by Adobe,
such as Adobe
XML Forms Architecture (XFA) and
for Acrobat, which are referenced by
ISO 32000-1 as normative and
indispensable for the full implementation of the
specification. These proprietary technologies are not standardized and
their specification is published only on Adobe’s
website. Many of them are also not supported by
popular third-party implementations of PDF.
On July 28, 2017,
ISO 32000-2 (PDF 2.0) was published by the ISO. ISO
32000-2 does not include any proprietary technologies as normative
The PDF combines three technologies:
A subset of the
PostScript page description programming language, for
generating the layout and graphics.
A font-embedding/replacement system to allow fonts to travel with the
A structured storage system to bundle these elements and any
associated content into a single file, with data compression where
PostScript is a page description language run in an interpreter to
generate an image, a process requiring many resources. It can handle
graphics and standard features of programming languages such as if and
loop commands. PDF is largely based on
PostScript but simplified to
remove flow control features like these, while graphics commands such
as lineto remain.
Often, the PostScript-like PDF code is generated from a source
PostScript file. The graphics commands that are output by the
PostScript code are collected and tokenized. Any files, graphics, or
fonts to which the document refers also are collected. Then,
everything is compressed to a single file. Therefore, the entire
PostScript world (fonts, layout, measurements) remains intact.
As a document format, PDF has several advantages over PostScript:
PDF contains tokenized and interpreted results of the PostScript
source code, for direct correspondence between changes to items in the
PDF page description and changes to the resulting page appearance.
PDF (from version 1.4) supports graphic transparency;
PostScript is an interpreted programming language with an implicit
global state, so instructions accompanying the description of one page
can affect the appearance of any following page. Therefore, all
preceding pages in a
PostScript document must be processed to
determine the correct appearance of a given page, whereas each page in
a PDF document is unaffected by the others. As a result, PDF viewers
allow the user to quickly jump to the final pages of a long document,
PostScript viewer needs to process all pages sequentially
before being able to display the destination page (unless the optional
Document Structuring Conventions have been carefully
A PDF file is a 7-bit
ASCII file, except for certain elements that may
have binary content. A PDF file starts with a header containing the
magic number and the version of the format such as %PDF-1.7. The
format is a subset of a COS ("Carousel" Object Structure) format.
A COS tree file consists primarily of objects, of which there are
Boolean values, representing true or false
Strings, enclosed within parentheses ((...)), may contain 8-bit
Names, starting with a forward slash (/)
Arrays, ordered collections of objects enclosed within square brackets
Dictionaries, collections of objects indexed by Names enclosed within
double pointy brackets (<<...>>)
Streams, usually containing large amounts of data, which can be
compressed and binary
The null object
Furthermore, there may be comments, introduced with the percent sign
(%). Comments may contain 8-bit characters.
Objects may be either direct (embedded in another object) or indirect.
Indirect objects are numbered with an object number and a generation
number and defined between the obj and endobj keywords. An index
table, also called the cross-reference table and marked with the xref
keyword, follows the main body and gives the byte offset of each
indirect object from the start of the file. This design allows for
efficient random access to the objects in the file, and also allows
for small changes to be made without rewriting the entire file
(incremental update). Beginning with PDF version 1.5, indirect objects
may also be located in special streams known as object streams. This
technique reduces the size of files that have large numbers of small
indirect objects and is especially useful for Tagged PDF.
At the end of a PDF file is a trailer introduced with the trailer
keyword. It contains
An offset to the start of the cross-reference table (the table
starting with the xref keyword)
And the %%EOF end-of-file marker.
The dictionary contains
A reference to the root object of the tree structure, also known as
The count of indirect objects in the cross-reference table
And other optional information.
There are two layouts to the PDF files: non-linear (not "optimized")
and linear ("optimized"). Non-linear PDF files consume less disk space
than their linear counterparts, though they are slower to access
because portions of the data required to assemble pages of the
document are scattered throughout the PDF file. Linear PDF files (also
called "optimized" or "web optimized" PDF files) are constructed in a
manner that enables them to be read in a Web browser plugin without
waiting for the entire file to download, since they are written to
disk in a linear (as in page order) fashion. PDF files may be
Adobe Acrobat software or QPDF.
The basic design of how graphics are represented in PDF is very
similar to that of PostScript, except for the use of transparency,
which was added in PDF 1.4.
PDF graphics use a device-independent
Cartesian coordinate system
Cartesian coordinate system to
describe the surface of a page. A PDF page description can use a
matrix to scale, rotate, or skew graphical elements. A key concept in
PDF is that of the graphics state, which is a collection of graphical
parameters that may be changed, saved, and restored by a page
description. PDF has (as of version 1.6) 24 graphics state properties,
of which some of the most important are:
The current transformation matrix (CTM), which determines the
The clipping path
The color space
The alpha constant, which is a key component of transparency
As in PostScript, vector graphics in PDF are constructed with paths.
Paths are usually composed of lines and cubic Bézier curves, but can
also be constructed from the outlines of text. Unlike PostScript, PDF
does not allow a single path to mix text outlines with lines and
curves. Paths can be stroked, filled, clipping. Strokes and fills can
use any color set in the graphics state, including patterns.
PDF supports several types of patterns. The simplest is the tiling
pattern in which a piece of artwork is specified to be drawn
repeatedly. This may be a colored tiling pattern, with the colors
specified in the pattern object, or an uncolored tiling pattern, which
defers color specification to the time the pattern is drawn. Beginning
with PDF 1.3 there is also a shading pattern, which draws continuously
varying colors. There are seven types of shading pattern of which the
simplest are the axial shade (Type 2) and radial shade (Type 3).
Raster images in PDF (called Image XObjects) are represented by
dictionaries with an associated stream. The dictionary describes
properties of the image, and the stream contains the image data. (Less
commonly, a raster image may be embedded directly in a page
description as an inline image.) Images are typically filtered for
compression purposes. Image filters supported in PDF include the
general purpose filters
ASCII85Decode a filter used to put the stream into 7-bit ASCII
ASCIIHexDecode similar to ASCII85Decode but less compact
FlateDecode a commonly used filter based on the deflate algorithm
defined in RFC 1951 (deflate is also used in the gzip, PNG, and zip
file formats among others); introduced in PDF 1.2; it can use one of
two groups of predictor functions for more compact zlib/deflate
compression: Predictor 2 from the
TIFF 6.0 specification and
predictors (filters) from the PNG specification (RFC 2083)
LZWDecode a filter based on
LZW Compression; it can use one of two
groups of predictor functions for more compact
Predictor 2 from the
TIFF 6.0 specification and predictors (filters)
from the PNG specification
RunLengthDecode a simple compression method for streams with
repetitive data using the run-length encoding algorithm and the
DCTDecode a lossy filter based on the
CCITTFaxDecode a lossless bi-level (black/white) filter based on the
Group 3 or Group 4
CCITT (ITU-T) fax compression standard defined in
T.4 and T.6
JBIG2Decode a lossy or lossless bi-level (black/white) filter based on
JBIG2 standard, introduced in PDF 1.4
JPXDecode a lossy or lossless filter based on the
JPEG 2000 standard,
introduced in PDF 1.5
Normally all image content in a PDF is embedded in the file. But PDF
allows image data to be stored in external files by the use of
external streams or Alternate Images. Standardized subsets of PDF,
PDF/A and PDF/X, prohibit these features.
Text in PDF is represented by text elements in page content streams. A
text element specifies that characters should be drawn at certain
positions. The characters are specified using the encoding of a
selected font resource.
A font object in PDF is a description of a digital typeface. It may
either describe the characteristics of a typeface, or it may include
an embedded font file. The latter case is called an embedded font
while the former is called an unembedded font. The font files that may
be embedded are based on widely used standard digital font formats:
Type 1 (and its compressed variant CFF), TrueType, and (beginning with
PDF 1.6) OpenType. Additionally PDF supports the Type 3 variant in
which the components of the font are described by PDF graphic
Standard Type 1 Fonts (Standard 14 Fonts)
Fourteen typefaces, known as the standard 14 fonts, have a special
significance in PDF documents:
Times (v3) (in regular, italic, bold, and bold italic)
Courier (in regular, oblique, bold and bold oblique)
Helvetica (v3) (in regular, oblique, bold and bold oblique)
These fonts are sometimes called the base fourteen fonts. These
fonts, or suitable substitute fonts with the same metrics, should be
available in most PDF readers, but they are not guaranteed to be
available in the reader, and may only display correctly if the system
has them installed. Fonts may be substituted if they are not
embedded in a PDF.
Within text strings, characters are shown using character codes
(integers) that map to glyphs in the current font using an encoding.
There are a number of predefined encodings, including WinAnsi,
MacRoman, and a large number of encodings for East Asian languages,
and a font can have its own built-in encoding. (Although the WinAnsi
and MacRoman encodings are derived from the historical properties of
the Windows and
Macintosh operating systems, fonts using these
encodings work equally well on any platform.) PDF can specify a
predefined encoding to use, the font's built-in encoding or provide a
lookup table of differences to a predefined or built-in encoding (not
TrueType fonts). The encoding mechanisms in PDF
were designed for Type 1 fonts, and the rules for applying them to
TrueType fonts are complex.
For large fonts or fonts with non-standard glyphs, the special
encodings Identity-H (for horizontal writing) and Identity-V (for
vertical) are used. With such fonts it is necessary to provide a
Unicode table if semantic information about the characters is to be
The original imaging model of PDF was, like PostScript's, opaque: each
object drawn on the page completely replaced anything previously
marked in the same location. In PDF 1.4 the imaging model was extended
to allow transparency. When transparency is used, new objects interact
with previously marked objects to produce blending effects. The
addition of transparency to PDF was done by means of new extensions
that were designed to be ignored in products written to the PDF 1.3
and earlier specifications. As a result, files that use a small amount
of transparency might view acceptably in older viewers, but files
making extensive use of transparency could be viewed incorrectly in an
older viewer without warning.
The transparency extensions are based on the key concepts of
transparency groups, blending modes, shape, and alpha. The model is
closely aligned with the features of
Adobe Illustrator version 9. The
blend modes were based on those used by
Adobe Photoshop at the time.
When the PDF 1.4 specification was published, the formulas for
calculating blend modes were kept secret by Adobe. They have since
The concept of a transparency group in PDF specification is
independent of existing notions of "group" or "layer" in applications
such as Adobe Illustrator. Those groupings reflect logical
relationships among objects that are meaningful when editing those
objects, but they are not part of the imaging model.
PDF files may contain interactive elements such as annotations, form
fields, video, 3D and rich media.
Rich Media PDF is a PDF file including interactive content that can be
embedded or linked within the file.
Interactive Forms is a mechanism to add forms to the PDF file format.
PDF currently supports two different methods for integrating data and
PDF forms. Both formats today coexist in PDF
AcroForms (also known as Acrobat forms), introduced in the PDF 1.2
format specification and included in all later PDF specifications.
XML Forms Architecture (XFA) forms, introduced in the PDF 1.5
format specification. Adobe
XFA Forms are not compatible with
XFA was deprecated from PDF with PDF 2.0.
AcroForms were introduced in the PDF 1.2 format. AcroForms permit
using objects (e.g. text boxes, Radio buttons, etc.) and some code
Alongside the standard PDF action types, interactive forms (AcroForms)
support submitting, resetting, and importing data. The "submit" action
transmits the names and values of selected interactive form fields to
a specified uniform resource locator (URL). Interactive form field
names and values may be submitted in any of the following formats,
(depending on the settings of the action’s ExportFormat, SubmitPDF,
and XFDF flags):
HTML Form format (
HTML 4.01 Specification since PDF 1.5;
Forms Data Format (FDF)
XML Forms Data Format (XFDF) (external
XML Forms Data Format
Specification, Version 2.0; supported since PDF 1.5; it replaced the
"XML" form submission format defined in PDF 1.4)
PDF (the entire document can be submitted rather than individual
fields and values). (defined in PDF 1.4)
AcroForms can keep form field values in external stand-alone files
containing key:value pairs. The external files may use Forms Data
Format (FDF) and
XML Forms Data Format (XFDF) files. The
usage rights (UR) signatures define rights for import form data files
in FDF, XFDF and text (CSV/TSV) formats, and export form data files in
FDF and XFDF formats.
Forms Data Format (FDF)
Forms Data Format (FDF)
Internet media type
1996 (1996) (PDF 1.2)
The Forms Data Format (FDF) is based on PDF, it uses the same syntax
and has essentially the same file structure, but is much simpler than
PDF, since the body of an FDF document consists of only one required
object. Forms Data Format is defined in the PDF specification (since
PDF 1.2). The Forms Data Format can be used when submitting form data
to a server, receiving the response, and incorporating into the
interactive form. It can also be used to export form data to
stand-alone files that can be imported back into the corresponding PDF
Beginning in PDF 1.3, FDF can be used to define a container for
annotations that are separate from the PDF document they apply to. FDF
typically encapsulates information such as
requests for certificates, directory settings, timestamp server
settings, and embedded PDF files for network transmission. The FDF
uses the MIME content type application/vnd.fdf, filename extension
.fdf and on Mac OS it uses file type 'FDF'.
XML Forms Data Format (XFDF)
XML Forms Data Format (XFDF)
Internet media type
July 2003 (2003-07) (referenced in PDF 1.5)
(August 2009; 8 years ago (2009-08))
PDF, FDF, XML
XFDF 3.0 specification
XML Forms Data Format (XFDF) is the
XML version of Forms Data Format,
but the XFDF implements only a subset of FDF containing forms and
annotations. There are not XFDF equivalents for some entries in the
keys, EmbeddedFDFs, Differences and Target. In addition, XFDF does not
allow the spawning, or addition, of new pages based on the given data;
as can be done when using an FDF file. The XFDF specification is
referenced (but not included) in PDF 1.5 specification (and in later
versions). It is described separately in
XML Forms Data Format
Specification. The PDF 1.4 specification allowed form submissions
XML format, but this was replaced by submissions in XFDF format in
the PDF 1.5 specification. XFDF conforms to the
As of December 2016, XFDF 3.0 is an ISO/IEC standard under the formal
ISO 19444-1:2016 –
Document management –
XML Forms Data
Format – Part 1: Use of
ISO 32000-2 (XFDF 3.0). This standard is
a normative reference of
XFDF can be used in the same way as FDF; e.g., form data is submitted
to a server, modifications are made, then sent back and the new form
data is imported in an interactive form. It can also be used to export
form data to stand-alone files that can be imported back into the
corresponding PDF interactive form.
XML Forms Architecture (XFA)
In PDF 1.5,
Adobe Systems introduced a proprietary format for forms;
XML Forms Architecture (XFA). Adobe
XFA Forms are not compatible
ISO 32000's AcroForms feature, and most PDF processors do not
XFA content. The
XFA specification is referenced from ISO
32000-1 / PDF 1.7 as an external proprietary specification, and was
entirely deprecated from PDF with
ISO 32000-2 (PDF 2.0).
Logical structure and accessibility
A "tagged" PDF (see clause 14.8 in
ISO 32000) includes document
structure and semantics information to enable reliable text extraction
and accessibility. Technically speaking, tagged PDF is a stylized use
of the format that builds on the logical structure framework
introduced in PDF 1.3. Tagged PDF defines a set of standard structure
types and attributes that allow page content (text, graphics, and
images) to be extracted and reused for other purposes.
Tagged PDF is not required in situations where a PDF file is intended
only for print. Since the feature is optional, and since the rules for
Tagged PDF were relatively vague in
ISO 32000-1, support for tagged
PDF amongst consuming devices, including assistive technology (AT), is
uneven at this time.
ISO 32000-2, however, includes an improved
discussion of tagged PDF which is anticipated to facilitate
An ISO-standardized subset of PDF specifically targeted at
accessibility; PDF/UA, was first published in 2012.
Optional Content Groups (layers)
With the introduction of PDF version 1.5 (2003) came the concept of
Layers. Layers, or as they are more formally known Optional Content
Groups (OCGs), refer to sections of content in a PDF document that can
be selectively viewed or hidden by document authors or consumers. This
capability is useful in CAD drawings, layered artwork, maps,
multi-language documents etc. Basically, it consists of an Optional
Content Properties Dictionary added to the document root. This
dictionary contains an array of Optional Content Groups (OCGs), each
describing a set of information and each of which may be individually
displayed or suppressed, plus a set of Optional Content Configuration
Dictionaries, which give the status (Displayed or Suppressed) of the
Security and signatures
A PDF file may be encrypted for security, or digitally signed for
authentication. However, since a SHA-1 collision was discovered making
use of the PDF format, digital signatures using SHA-1 have been shown
to be insecure.
The standard security provided by Acrobat PDF consists of two
different methods and two different passwords: a user password, which
encrypts the file and prevents opening, and an owner password, which
specifies operations that should be restricted even when the document
is decrypted, which can include modifying, printing, or copying text
and graphics out of the document, or adding or modifying text notes
and AcroForm fields. The user password encrypts the file, while the
owner password does not, instead relying on client software to respect
these restrictions. An owner password can easily be removed by
software, including some free online services. Thus, the use
restrictions that a document author places on a PDF document are not
secure, and cannot be assured once the file is distributed; this
warning is displayed when applying such restrictions using Adobe
Acrobat software to create or edit PDF files.
Even without removing the password, most freeware or open source PDF
readers ignore the permission "protections" and allow the user to
print or make copy of excerpts of the text as if the document were not
limited by password protection.
There are a number of commercial solutions that offer more robust
means of information rights management. Not only can they restrict
document access but they also reliably enforce permissions in ways
that the standard security handler does not.
Beginning with PDF 1.5, Usage rights (UR) signatures are used to
enable additional interactive features that are not available by
default in a particular PDF viewer application. The signature is used
to validate that the permissions have been granted by a bona fide
granting authority. For example, it can be used to allow a user:
To save the PDF document along with modified form and/or annotation
Import form data files in FDF, XFDF, and text (CSV/TSV) formats
Export form data files in FDF and XFDF formats
Submit form data
Instantiate new pages from named page templates
Apply a digital signature to existing digital signature form field
Create, delete, modify, copy, import, and export annotations
Adobe Systems grants permissions to enable additional
features in Adobe Reader, using public-key cryptography. Adobe Reader
verifies that the signature uses a certificate from an
Adobe-authorized certificate authority. Any PDF application can use
this same mechanism for its own purposes.
PDF files can have file attachments which processors may access and
open or save to a local filesystem.
PDF files can contain two types of metadata. The first is the
Document Information Dictionary, a set of key/value fields such as
author, title, subject, creation and update dates. This is stored in
the optional Info trailer of the file. A small set of fields is
defined, and can be extended with additional text values if required.
This method is deprecated in PDF 2.0.
In PDF 1.4, support was added for
Metadata Streams, using the
Extensible Metadata Platform (XMP) to add
extensible metadata as used in other file formats. This allows
metadata to be attached to any stream in the document, such as
information about embedded illustrations, as well as the whole
document (attaching to the document catalog), using an extensible
Usage restrictions and monitoring
PDFs may be encrypted so that a password is needed to view or edit the
contents. PDF 2.0 defines 256-bit AES encryption as standard for PDF
2.0 files. The PDF Reference also defines ways that third parties can
define their own encryption systems for PDF.
PDF files may be digitally signed; complete details on implementing
digital signatures in PDF is provided in
PDF files may also contain embedded DRM restrictions that provide
further controls that limit copying, editing or printing. These
restrictions depend on the reader software to obey them, so the
security they provide is limited.
Default display settings
PDF documents can contain display settings, including the page display
layout and zoom level. Adobe Reader uses these settings to override
the user's default settings when opening the document. The free
Adobe Reader cannot remove these settings.
Anyone may create applications that can read and write PDF files
without having to pay royalties to Adobe Systems; Adobe holds patents
to PDF, but licenses them for royalty-free use in developing software
complying with its PDF specification.
PDF files can be created specifically to be accessible for disabled
people. PDF file formats in use as of 2014[update]
can include tags, text equivalents, captions, audio descriptions, and
more. Some software can automatically produce tagged PDFs, but this
feature is not always enabled by default. Leading screen
readers, including JAWS, Window-Eyes, Hal, and Kurzweil 1000 and 3000
can read tagged PDF. Moreover, tagged PDFs can be re-flowed
and magnified for readers with visual impairments. Adding tags to
older PDFs and those that are generated from scanned documents can
present some challenges.
One of the significant challenges with PDF accessibility is that PDF
documents have three distinct views, which, depending on the
document's creation, can be inconsistent with each other. The three
views are (i) the physical view, (ii) the tags view, and (iii) the
content view. The physical view is displayed and printed (what most
people consider a PDF document). The tags view is what screen readers
and other assistive technologies use to deliver a high-quality
navigation and reading experience to users with disabilities. The
content view is based on the physical order of objects within the
PDF's content stream and may be displayed by software that does not
fully support the tags view, such as the Reflow feature in Adobe's
PDF/UA, the International Standard for accessible PDF based on ISO
32000-1 was first published as
ISO 14289-1 in 2012, and establishes
normative language for accessible PDF technology.
Viruses and exploits
Adobe Acrobat § Security
PDF attachments carrying viruses were first discovered in 2001. The
virus, named OUTLOOK.PDFWorm or Peachy, uses
Microsoft Outlook to send
itself as an attachment to an Adobe PDF file. It was activated with
Adobe Acrobat, but not with Acrobat Reader.
From time to time, new vulnerabilities are discovered in various
versions of Adobe Reader, prompting the company to issue security
fixes. Other PDF readers are also susceptible. One aggravating factor
is that a PDF reader can be configured to start automatically if a web
page has an embedded PDF file, providing a vector for attack. If a
malicious web page contains an infected PDF file that takes advantage
of a vulnerability in the PDF reader, the system may be compromised
even if the browser is secure. Some of these vulnerabilities are a
result of the PDF standard allowing PDF documents to be scripted with
mitigate such future exploits, although it does not protect against
exploits in other parts of the PDF viewing software. Security experts
security benefit that comes from disabling
compatibility issues caused. One way of avoiding PDF file exploits
is to have a local or web service convert files to another format
On March 30, 2010 security researcher Didier Stevens reported an Adobe
Foxit Reader exploit that runs a malicious executable if
the user allows it to launch when asked.
A PDF file is often a combination of vector graphics, text, and bitmap
graphics. The basic types of content in a PDF are:
Text stored as content streams (i.e., not encoded in plain text)
Vector graphics for illustrations and designs that consist of shapes
Raster graphics for photographs and other types of image
Multimedia objects in the document
In later PDF revisions, a PDF document can also support links (inside
document or web page), forms,
plugin for Acrobat 3.0), or any other types of embedded contents that
can be handled using plug-ins.
PDF 1.6 supports interactive 3D documents embedded in the PDF – 3D
drawings can be embedded using
U3D or PRC and various other data
Two PDF files that look similar on a computer screen may be of very
different sizes. For example, a high resolution raster image takes
more space than a low resolution one. Typically higher resolution is
needed for printing documents than for displaying them on screen.
Other things that may increase the size of a file is embedding full
fonts, especially for Asiatic scripts, and storing text as graphics.
Further information: List of PDF software
PDF viewers are generally provided free of charge, and many versions
are available from a variety of sources.
There are many software options for creating PDFs, including the PDF
printing capabilities built into macOS, iOS, and most Linux
Microsoft Office 2007
Microsoft Office 2007 (if updated to SP2)
WordPerfect 9, Scribus, numerous PDF print drivers for
Microsoft Windows, the pdf
TeX typesetting system, the
tools, applications developed around
Ghostscript and Adobe Acrobat
itself as well as Adobe InDesign, Adobe FrameMaker, Adobe Illustrator,
Adobe Photoshop. Google's online office suite
Google Docs also allows
for uploading and saving to PDF.
Raster image processors (RIPs) are used to convert PDF files into a
raster format suitable for imaging onto paper and other media in
printers, digital production presses and prepress in a process known
as rasterisation. RIPs capable of processing PDF directly include the
Adobe PDF Print Engine from
Adobe Systems and Jaws and the
Harlequin RIP from Global Graphics.
This section needs expansion. You can help by adding to it. (July
Adobe Illustrator reads and writes PDF as a semi-native format. With
multipage documents, a dialog opens enabling the user to select a
single page to edit. Editing paragraphs of text typically disturbs
line justification and paragraph wrapping, as multiline text is
converted to individual lines. In a multipage document, only the page
being edited can be re-saved.
Inkscape version 0.46 and later allows PDF editing of a single page
through an intermediate translation step involving Poppler, then
document can be exported again as PDF.
Scribus allows opening and editing multi-page PDF, then document can
be exported again as PDF.
LibreOffice Draw and
Apache OpenOffice Draw (using a plugin PDFimport)
can open and edit multi-page PDF, then document can be exported again
Serif PagePlus can open, edit and save existing PDF documents, as well
as publishing of documents created in the package.
Enfocus PitStop Pro, a plugin for Acrobat, allows manual and automatic
editing of PDF files, while the free
Enfocus Browser makes it
possible to edit the low-level structure of a PDF.
Dochub, is a free online PDF editing tool that can be used without
See also: Comparison of notetaking software
Adobe Acrobat is one example of proprietary software that allows the
user to annotate, highlight, and add notes to already created PDF
files. One UNIX application available as free software (under the GNU
General Public License) is PDFedit. Another GPL-licensed application
native to the unix environment is Xournal. Xournal allows for
annotating in different fonts and colours, as well as a rule for
quickly underlining and highlighting lines of text or paragraphs.
Xournal also has a shape recognition tool for squares, rectangles and
circles. In Xournal annotations may be moved, copied and pasted. The
freeware Foxit Reader, available for
Microsoft Windows, macOS and
Linux, allows annotating documents. Tracker Software's PDF-XChange
Viewer allows annotations and markups without restrictions in its
freeware alternative. Apple's macOS's integrated PDF viewer, Preview,
does also enable annotations as does the open source software Skim,
with the latter supporting interaction with LaTeX, SyncTeX, and
PDFSync and integration with
BibDesk reference management software.
Qiqqa can create an annotation report that summarizes all the
annotations and notes one has made across their library of PDFs.
For mobile annotation, iAnnotate PDF (from Branchfire) and GoodReader
(from Aji) allow annotation of PDFs as well as exporting summaries of
There are also web annotation systems that support annotation in pdf
and other documents formats, e.g., A.nnotate, crocodoc, WebNotes.
In cases where PDFs are expected to have all of the functionality of
paper documents, ink annotation is required. Some programs that accept
ink input from the mouse may not be responsive enough for handwriting
input on a tablet. Existing solutions on the PC include PDF Annotator
Examples of PDF software as online services including
viewing and storing,
Pdfvue for online editing, and
In 1993 the Jaws raster image processor from Global
the first shipping prepress RIP that interpreted PDF natively without
conversion to another format. The company released an upgrade to their
Harlequin RIP with the same capability in 1997.
Agfa-Gevaert introduced and shipped Apogee, the first prepress
workflow system based on PDF, in 1997.
Many commercial offset printers have accepted the submission of
press-ready PDF files as a print source, specifically the PDF/X-1a
subset and variations of the same. The submission of press-ready
PDF files are a replacement for the problematic need for receiving
collected native working files.
PDF was selected as the "native" metafile format for Mac OS X,
PICT format of the earlier classic Mac OS. The imaging
model of the Quartz graphics layer is based on the model common to
PostScript and PDF, leading to the nickname Display PDF. The
Preview application can display PDF files, as can version 2.0 and
later of the Safari web browser. System-level support for PDF allows
Mac OS X applications to create PDF documents automatically, provided
they support the OS-standard printing architecture. The files are then
exported in PDF 1.3 format according to the file header. When taking a
screenshot under Mac OS X versions 10.0 through 10.3, the image was
also captured as a PDF; later versions save screen captures as a PNG
file, though this behaviour can be set back to PDF if desired.
In 2006 PDF was widely accepted as the standard print job format at
Open Source Development Labs Printing Summit. It is supported as a
print job format by the Common Unix Printing System and desktop
application projects such as GNOME, KDE, Firefox, Thunderbird,
LibreOffice and OpenOffice have switched to emit print jobs in
Some desktop printers also support direct PDF printing, which can
interpret PDF data without external help. Currently, all PDF capable
printers also support PostScript, but most
PostScript printers do not
support direct PDF printing.
Free Software Foundation
Free Software Foundation once considered one of their high
priority projects to be "developing a free, high-quality and fully
functional set of libraries and programs that implement the PDF file
format and associated technologies to the
ISO 32000 standard."
In 2011, however, the GNU PDF project was removed from the list of
"high priority projects" due to the maturation of the Poppler
library, which has enjoyed wider use in applications such as
Evince with the
GNOME desktop environment. Poppler is based on
Xpdf code base. There are also commercial development
libraries available as listed in List of PDF software.
Apache PDFBox project of the
Apache Software Foundation
Apache Software Foundation is an open
source Java library for working with PDF documents. PDFBox is licensed
under the Apache License.
XML Paper Specification
Comparison of OpenXPS and PDF
PAdES, PDF Advanced Electronic Signature
XSL Formatting Objects
Adobe Acrobat and Portable
Document Format, file extension
.pdf was used by a word processor named WordStar, which used this
extension for printer definition files.
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PDF 1.7 
PDF 1.6 (ISBN 0-321-30474-8)
PDF 1.4 (ISBN 0-201-75839-3)
PDF 1.3 (ISBN 0-201-61588-6)
Wikimedia Commons has media related to Portable
How was the PDF format created? Quora
PDF Association – The PDF Association is the industry association
for software developers producing or processing PDF files.
Adobe PDF 101: Summary of PDF
PostScript vs. PDF – Official introductory comparison of PS,
EPS vs. PDF.
PDF Standards... transitioning the PDF specification from a de facto
standard to a de jure standard at the
Wayback Machine (archived April
24, 2011) – Information about
PDF/UA specification for
accessible documents file format (archived by The Wayback Machine)
ISO 19005-1:2005 the PDF/A-1
ISO standard published by the
International Organization for Standardization
International Organization for Standardization (chargeable)
PDF Reference and Adobe Extensions to the PDF Specification
Document Format: An Introduction for Programmers –
Introduction to PDF vs.
PostScript and PDF internals (up to v1.3)
The Camelot Paper – the paper in which John Warnock outlined the
project that created PDF
Everything you wanted to know about PDF but were afraid to ask –
recording of talk by Leonard Rosenthol (Adobe Systems) at TUG 2007
How to produce PDF with XSL-FO
PDF To Excel Converter
Graphics file formats
ICO / CUR
PBM / PGM / PPM / PNM
PSD / PSB
Exchangeable image file format (Exif)
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Multi-purpose office document file formats
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Office Open XML
Rich Text Format
Uniform Office Format
Fixed document formats
XML Paper Specification
ISO standards by standard number
ISO standards /
ISO romanizations / IEC standards
Barnes & Noble Nook
Plastic Logic Reader
Adobe Digital Editions
Google Play Books
OverDrive Media Console
Atlantis Word Processor
Help & Manual
Amazon Kindle Store
Baen Free Library
Barnes & Noble
Sony Reader Store
Academic journal publishing reform
Comparison of e-book readers
Comparison of iOS e-book reader software
Comparison of Android e-book reader software
iBooks Author Conference
International Digital Publishing Forum