Duff Johnson’s PDF Perspective

Readers may recall that a few months ago I was contacted by a writer for the magazine now known as Mac|Life (formerly MacAddict) for a review of Adobe Acrobat 8.0 Professional.

While I offered a number of thoughts at the time, few made it into the April issue, which isn’t surprising - I can be very long-winded.

More interesting (frankly) is the proportion of space allocated to Connect, a rebranded Macromedia product unrelated to Acrobat.  So why spend most of a review of Acrobat talking about Connect?  The only “connection” between Acrobat and Connect is a link to the Connect website from the Acrobat toolbar, so Adobe’s marketing folks clearly know their business.

Rather than read my carping about misguided editorial (and other) judgments, I’ll let you decide for yourself. Here’s the piece (PDF, 180 kb).

PDF was originally designed to do one thing: deliver an author’s intent to screen or printer in an efficient, precise and platform-independent manner. This “print paradigm” persists today, and colors the issue of accessible PDF in subtle but pervasive ways.

To understand how the print orientation in PDF presents a challenge to accessibility, begin with the fact that a PDF has no intrinsic notion of words or paragraphs.

PDF “thinks” like a printer “thinks”. Objects (such as text, images, lines, etc.) appearing on the page are considered in terms of precise location and sequence of appearance, not their semantic relationship to one another. Words and paragraphs aren’t useful constructs in printing, for they offer no assistance in the placement of ink.  As a consequence, the very concept of a word was literally missing from PDF until 2000, when Adobe published the basic mechanism for “structured” PDF with the PDF Reference 1.3.

What is structured PDF?  Simply put, it is PDF with additional information to organize the objects on the page into words, lines and paragraphs, and to order these larger blocks of content into a “text flow”.

In late 2001, Adobe published the PDF Reference 1.4, which described ”tagged” pdf, adding organization and nomenclature to the structure elements.

Tags allow the author to manage text-flow, define headings, add alternate text to images, ensure tables match the intent, and generally ensure that the document contents are fully and discreetly available to users who can benefit from such information.

Who are these comsumers of of structured and tagged PDF?  They include disabled and other AT (assistive technology) users, but anyone trying to copy-and-paste text or read a PDF on a mobile device will prefer tagged to untagged PDF.

Beyond strictly human “users”, tagged PDF improves search engine results, and even makes possible the extension of semantic Web concepts to PDF.

Those interested in more specific or technical information should check out Mark Gavin’s presentation, PDF and Accessibility (PDF, 857 kb), at labs.appligent.com.

In a forthcoming post, I’ll lay out the business case for better tools to enhance PDF accessibility.

The PDF/Universal Accessibility (PDF/UA) Committee met at the AIIM Conference and Expo in Boston this past week.  If you are interested, you can read the agenda from the public portion of PDF/UA’s Wiki.

We welcomed new members and had a productive day-and-a-half of meetings covering a wide range of issues, from MathML to table structure, multimedia and programmatic validation.

For those who don’t know about PDF/UA, we are a Standards Committee of AIIM, tasked with the mission of developing a draft ISO specification defining what it means to create and validate a PDF as “accessible”.

Accessibility isn’t just about screen-readers for blind and other disabled users. Accessible PDF is more usable, more navigable, friendlier to search engines and reflows smoothly onto mobile screens.  If you or your organization has an interest in the multifaceted opportunities for enhancing end-user experience of electronic content, I invite you to come join PDF/UA for one of our regular teleconference meetings!