PDF 2.0 - A quick overview

It is rare for industrial products to survive for more than 20 years – especially in the IT industry. Not even the inventors of the PDF could have imagined just how successful their file format would be when they launched the first version of Acrobat in June 1993. The members of the International Organization for Standardization (ISO) have been working on the next generation of this popular format.

Since ISO-32000-1, entitled “Document Management – Portable Document Format– Part 1: PDF 1.7”, was published in mid-2008, the sixth edition of Adobe’s famous PDF Reference has not changed significantly – just translated into the ISO language. But this has changed with the second part of the standard, “Part 2: PDF 2.0”, which has been published recently. This new version has been created by the ISO members, or to be precise by Technical Committee 171, Sub-committee 2. To make it clear that this is a new standard, a ‘2’ has been added to the main version number.

The list of changes contains more than 50 entries. The most important changes and improvements relate to the following areas:

• Encryption: unencrypted wrapper of encrypted documents, 256-bit AES encryption, unicode passwords

• Digital signatures: signatures based on the CAdES standard, certificates based on elliptic curves, long-term signature validation (LTV)

• Annotations: projections, 3D, rich media

• Accessibility: pronunciation hints

• 3D: support for the new ISO standard ‘PRC’, 3D measurements

• Document parts (introduced in PDF/VT)

The committee has also been brave enough to scrap some outdated features; the main ones are:

• XFA forms: Adobe’s XML-based form technology has been a constant source of frustration for many providers

• Movie, sound: multimedia content is not compatible with the concept of a portable document format

• Superfluous, redundant, outdated or non-portable information, such as the document information dictionary (replaced by XMP), outdated digital signatures, OS-dependent file names and rarely used standards, such as OPI (Open Prepress Interface)

There have also been some major revisions to the new part of the standard, particularly in the following chapters:

• Rendering

• Transparency

• Digital signatures

• Metadata

• Tagged PDF and accessibility Support

But the numerous changes have taken their toll. It has taken seven years to create the second part, much longer than was needed for previous versions. In fact, Adobe managed to release seven versions in just 15 years – and in outstanding quality. On the plus side, the second part of the standard has received extensive input from the ISO members, and many parts of the text are worded more clearly. This makes it easier for the industry to understand the specification, increase the implementation quality and thereby improve interoperability. It is hoped that this will result in far fewer ‘bad’ PDFs.

For the main uses of PDF – i.e. archiving (PDF/A), document exchange (PDF/X), engineering (PDF/E) and accessibility (PDF/UA) – ISO has defined special sub-standards, most of which are based on the first part of the PDF standard. It is likely that these standards will also be adapted to make them relevant to the second part. However, it should not be assumed that the master standard will now be ‘new’ and the sub-standards ‘old’.

Instead, the development of these standards should be seen as an interaction. For example, many changes in the second part of the PDF standard are based on findings derived from working on the sub-standards and incorporated in the development. In addition – unlike the PDF master standard – there is no real urgency to change the PDF/X, PDF/E and PDF/UA sub-standards, as they have been optimized independently of Adobe for some time now. However, the situation for PDF/A is somewhat different.

As soon as the first Version 2.0 PDF files are created, the question will arise as to how they can be archived in accordance with the standard. PDF/A must have an answer to this question. Unlike the other PDF sub-standards, this application is under a certain degree of time pressure. But the sheer number of changes is making it difficult to find a quick solution.

The PDF 2.0 standard is still very young and there are hardly any files in circulation. Time will tell if the standard will work and how quickly manufacturers will implement it.