Over the years the Portable Document Format has evolved enormously. This page lists all the major releases, starting from PDF 1.0 which was released in 1993. For each PDF version the new features are listed. A more elaborate overview of the history of PDF can be found here.
Overall the PDF file format is remarkably flexible: obviously it is forward compatible, allowing you to open an old PDF 1.0 file in the latest version of the Adobe Reader. Backwards compatibility is also pretty good: a recent PDF 1.7 file can be opened by Acrobat 4. The older software will ignore the newer features and may not be able to display page elements that use them.
Availability: November 1992 (announcement)/June 1993 (first software)
Matching software: Adobe Acrobat 1.0
Availability: November 1994
Matching software: Adobe Acrobat 2.0
- External links – embed a link to external documents or URLs.
- Article threads – articles that span multiple columns or pages are linked so that readers can easily navigate the text.
- Security features- protect PDF files by a password.
- Device independent color – PDF 1.0 only supported RGB, which left quite some room for improvement.
Availability: November 1996
Matching software: Adobe Acrobat 3.0
- Forms – allow users to add data to a PDF or use a PDF as an electronic form.
- Unicode – use extended character sets.
- Multimedia features – adding interactive page elements such as mouse events and support for additional multimedia types .
- Support for the OPI 1.3 specifications
- Improved color support – both the CMYK color space and spot colors can be used.
- Halftone functions as well as overprint instructions can be embedded.
Availability: April 1999
Matching software: Adobe Acrobat 4.0
- 2-byte CID fonts
- Support for OPI 2.0
- Additional color spaces – ICC-based colors are supported. A new color space called DeviceN improves support for spot colors.
- Smooth shading, a technology that allows for efficient and very smooth blends (transitions from one color or tint to another).
- Digital signatures
- RC4 encryption – 40 bit (Acrobat 4) & 56 bit (Acrobat 4.05)
Availability: May 2001
Matching software: Adobe Acrobat 5.0
- Support for Tagged PDF – Tagged PDF files also contain structural information about the data that are representated by the PDF document. This means that meta-information like defining titles, blocks of text,… can be part of a PDF-document.
- JBIG2 compression
- 128-bit RC4 encryption
Availability: April 2003
Matching software: Adobe Acrobat 6.0 & Adobe Reader 6.0
- Improved compression techniques including object streams & JPEG 2000 compression
- enhanced XRef table – XRef streams, support for more objects,…
- Support for layers
- Improved support for tagged PDF
- XFA – XFA is the abbreviation to XML Forms Architecture.
- 12 additional transitions when using PDF pages for presentations.
Availability: January 2005
Matching software: Adobe Acrobat 7.0 & Adobe Reader 7.0
- NChannel – an extension of the DeviceN mechanism for defining spot colors.
- AES encryption
- Some minor enhancements to annotations and tagging
- Direct embedding of OpenType fonts – these no longer have to be embedded as TrueType or Type 1 fonts.
- PDF 1.6 files can be used as a kind of ‘container’ file format by offering the possibility to embed files into a PDF.
- Embedding 3D data (U3D) – a useful addition for engineers but also for the packaging and display markets.
- XML forms
Availability: October 2006
Matching software: Adobe Acrobat 8.0 & Adobe Reader 8.0
- Improved support for commenting and security.
- Add comments to 3D-objects and more elaborate control over 3D animations.
- Embed default printer settings such as paper selection, number of copies and scaling.
Adobe extension levels
Since Adobe handed over the PDF standard to the ISO organisation, they can no longer release new versions of the file format. To still have the ability to extend it, they now add custom features to PDF that only their own software supports. Obviously Adobe strive to have ISO accept these enhancements as new features of an upcoming new version of the PDF specifications.
Extension level 3
Matching software: Adobe Acrobat 9.0 & Adobe Reader 9.0
New features: 256-bit AES encryption
Extension level 5
Matching software: Adobe Acrobat 9.1 & Adobe Reader 9.1
New features: XFA 3.0 – an update for the XML Forms Architecture.