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From Wikipedia, the free encyclopedia
For other uses, see PDF (disambiguation).
Portable Document Format
Adobe PDF icon
Filename .pdf
extension
application/pdf ,[1]
Internet
media type application/x-pdf
application/x-bzpdf
application/x-gzpdf
Type code PDF [1] (including a single trailing
space)
Uniform Type com.adobe.pdf
Identifier (UTI)
Magic number %PDF
Developed by Adobe Inc. (1991–2008)
ISO (2008–)
Initial release June 15, 1993; 32 years ago
Latest release 2.0
Extended to PDF/A, PDF/E, PDF/UA, PDF/VT, PDF/X
Standard ISO 32000-2
Open format? Yes
Website iso.org/standard/75839.html
Portable Document Format (PDF), standardized as ISO 32000, is a file
format developed by Adobe in 1992 to present documents, including text formatting and
images, in a manner independent of application software, hardware, and operating
systems.[2][3] 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 has its roots in
"The Camelot Project" initiated by Adobe co-founder John Warnock in 1991.[4] PDF was
standardized as ISO 32000 in 2008.[5] It is maintained by ISO TC 171 SC 2 WG8, of
which the PDF Association is the committee manager.[6] The last edition as ISO 32000-
2:2020 was published in December 2020.[7]
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), three-dimensional objects
using U3D or 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 features.
History
Main article: History of PDF
The development of PDF began in 1991 when John Warnock wrote a paper for a
project then code-named Camelot, in which he proposed the creation of a simplified
version of PostScript called Interchange PostScript (IPS).[8] Unlike traditional PostScript,
which was tightly focused on rendering print jobs to output devices, IPS would be
optimized for displaying pages to any screen and any platform.[8]
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 several other formats, including DjVu, Envoy, Common Ground Digital Paper,
Farallon Replica and even Adobe's own PostScript format.
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 as ISO 32000-1:2008,[9][10] at which time control of the specification
passed to an 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 necessary to make, use, sell, and distribute PDF-compliant
implementations.[11]
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 JavaScript extension for Acrobat, which are referenced by ISO
32000-1 as normative and indispensable for the full implementation of the ISO 32000-1
specification.[12] These proprietary technologies are not standardized, and their
specification is published only on Adobe's website.[13][14][15] Many of them are not
supported by popular third-party implementations of PDF.
ISO published version 2.0 of PDF, ISO 32000-2 in 2017, available for purchase,
replacing the free specification provided by Adobe.[16] In December 2020, the second
edition of PDF 2.0, ISO 32000-2:2020, was published, with clarifications, corrections,
and critical updates to normative references[17] (ISO 32000-2 does not include any
proprietary technologies as normative references).[18] In April 2023 the PDF Association
made ISO 32000-2 available for download free of charge.[16]
Technical details
A PDF file is often a combination of vector graphics, text, and bitmap graphics. The
basic types of content in a PDF are:
Typeset text stored as content streams (i.e., not encoded in plain text);
Vector graphics for illustrations and designs that consist of shapes and lines;
Raster graphics for photographs and other types of images; and
Other multimedia objects.
In later PDF revisions, a PDF document can also support links (inside document or web
page), forms, JavaScript (initially available as a plugin for Acrobat 3.0), or any other
types of embedded contents that can be handled using plug-ins.
PDF combines three technologies:
An equivalent subset of the PostScript page description programming language but in
declarative form, for generating the layout and graphics.
A font-embedding/replacement system to allow fonts to travel with the documents.
A structured storage system to bundle these elements and any associated content into a
single file, with data compression where appropriate.
PostScript language
PostScript is a page description language run in an interpreter to generate an image.[8] It
can handle graphics and has standard features of programming languages such
as branching and looping.[8] PDF is a subset of PostScript, simplified to remove
such control flow features, while graphics commands remain.[8]
PostScript was originally designed for a drastically different use case: transmission of
one-way linear print jobs in which the PostScript interpreter would collect a series of
commands until it encountered the showpage command, then execute all the commands
to render a page as a raster image to a printing device.[19] PostScript was not intended
for long-term storage and real-time interactive rendering of electronic
documents to computer monitors, so there was no need to support anything other than
consecutive rendering of pages.[19] If there was an error in the final printed output, the
user would correct it at the application level and send a new print job in the form of an
entirely new PostScript file. Thus, any given page in a PostScript file could be
accurately rendered only as the cumulative result of executing all preceding commands
to draw all previous pages—any of which could affect subsequent pages—plus the
commands to draw that particular page, and there was no easy way to bypass that
process to skip around to different pages.[19]
Traditionally, to go from PostScript to PDF, a source PostScript file (that is, an
executable program) is used as the basis for generating PostScript-like PDF code (see,
e.g., Adobe Distiller). This is done by applying standard compiler techniques like loop
unrolling, inlining and removing unused branches, resulting in code that is purely
declarative and static.[19] The result is then packaged into a container format, together
with all necessary dependencies for correct rendering (external files, graphics, or fonts
to which the document refers), and compressed. Modern applications write to printer
drivers that directly generate PDF rather than going through PostScript first.
As a document format, PDF has several advantages over PostScript:
PDF contains only static declarative PostScript code that can be processed as data, and
does not require a full program interpreter or compiler.[19] This avoids the complexity and
security risks o
