PDF In-Depth

Is PDF an open standard?

About the Author
Duff Johnson picture

Duff Johnson

Since 2011, Duff has worked in the ECM industry specializing in PDF technology since 1995. An industry leader, Duff co-chairs the international committee that manages ISO 32000, the specification for the PDF file format. Responsible for marketing and product...  More



Editor's Note: Duff Johnson is the CEO of Appligent Document Solutions. This article originally appeared on Appligent.com, and has been reprinted with permission.

On May 13, the founders of Adobe Systems stepped up to the microphone to deliver a response to Steve Jobs' open letter about Flash. They say Adobe has acted on open standards while Apple offers mere words.

At the outset, I must acknowledge that I owe my livelihood to the genius of these two gentlemen. The inventors of PostScript and PDF and the creators of Adobe Systems, Warnock and Geschke are gods in my Pantheon. They are the founding fathers of technologies that have been instrumental in making computers relevant to the modern everyday operations of government and business.

That said, claims about PDF being a true open standard need to be placed in context.

Yes, PDF is an open standard

Adobe Systems has published the PDF Reference, the rulebook for PDF developers, since 1993. At the very beginning, if you wanted to make, view or manipulate PDFs you bought the book in the store for a few dollars. Pretty soon it was (and still is) available online at no charge.

On July 1, 2008, version 1.7 of the PDF Reference was rewritten as ISO 32000, a document managed by committees under the auspices of the International Standards Organization. ISO 32000 is managed by individual representatives of interested parties in open meetings under parliamentary rules. Anyone can observe and participate. While they are obviously heavily invested in the outcome of the committee's decisions, Adobe Systems has only one vote at the table, the same as any other.

By now, the rulebook for PDF is relatively mature and precise in its language. It was not always so. Adobe's very openness -- their willingness to let third-parties in to make their own PDFs before the PDF Reference was a mature document -- was and continues to be a source of pain.

Welcome to the real world

When millions of PDF files from hundreds of different applications started flying around, two major problems with the rulebook for PDF emerged.

First, while the Reference set rules it is not a cookbook; it included no recipes for how to create content on a PDF page.

Second, the Reference was ambiguous in some areas and left other matters under-considered, sometimes unaddressed.

When dealing with real-world documents, Adobe's software had to deal with these vagaries, so more rules were written; specific details of their implementation were crafted to address the issues encountered in the real world.

These new rules, however, were in the software, not the Reference. As the Reference developed, Adobe's implementation and the published rules began to diverge. It became possible to create a "legal" PDF file that otherwise perfectly serviceable software couldn't handle quite right (or handled dead wrong). In fact, because the early versions of the PDF Reference were so vague (relatively speaking), the range of possible oddities that were legal in a PDF was very wide indeed. A lot of sloppy PDF software was (and still is) written for this reason.

Example of a PDF rendering error.

Three of five PDF viewers displayed this PDF incorrectly.

I remember discussing this problem with Adobe developers in the late 1990s. First and foremost, we all knew PDF had to be reliable. PDFs had to display the same way on-screen and in-print, no matter the platform. The problem with these "legal" but otherwise oddball PDF files was that if they displayed with problems in Adobe Reader, then Adobe (not the PDF's producer) would get the blame.

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