by Duff Johnson
Over nine years ago, we were first in the world to offer tagging and Section 508 compliance services for PDF files.
So you can imagine that we’ve been very, very interested in the subject of accessibility checker software for PDF files for a very long time.
Until recently, Adobe Acrobat Professional’s Accessibility Checker was the only game in town, and that game hasn’t moved in years. The last significant update to Acrobat’s tagging tools was in Acrobat 7, which shipped back in January, 2005.
Astute observers will notice the distinct lack of any updates on the tagging front in the just-announced Acrobat X. As a beta-tester of the software I can assure you that if Acrobat X included improvements to the tagging tools, Adobe’s Acrobat X marketing would say so, and it doesn’t.
If Acrobat’s PDF tagging tools development has stalled, what of other vendors? Net-Centric’s Acrobat plugin, CommonLook, provides superior table-tagging tools and other options that improve on Acrobat. Nonetheless, the marketplace has so far failed to deliver a quick, easy and inexpensive way for end-users to understand what’s wrong (or sub-optimal) in their tagged PDF.
Enter the PDF Accessibility Checker (PAC)
It was for this reason that we were so pleased to find the “PAC”, or PDF Accessibility Checker, free software by Access for All, a Swiss non-profit foundation.
PAC is a pretty interesting, and did I mention that it’s FREE?
The fundamental value of the tool as compared with Acrobat is the Preview feature, which displays the tagged content in tag order (as is only right & proper), with nice little labels when you hover over the tags. Apart from instantly being able to visualize the way in which your document appears to an Assistive Technology (AT) user, this Preview provides a quick and effective debugging tool, allowing you to quickly locate and therefore (back in Acrobat) fix your PDF’s tags, mark as Artifact, or other.
While superficially similar, this feature is NOT to be confused with Acrobat’s “Reflow” feature, which is nearly useless, from an accessibility perspective. (More on that in another article)
CommonLook also offers a tags-based Preview, but CommonLook isn’t free, and requires Adobe Acrobat. With PAC, any user can immediately see if their PDF is usefully tagged or not.
The PAC checks for a Title, promotes the use of bookmarks and section header tags, checks for contrast, and much more. It’s head-and-shoulders above Acrobat’s Accessibility Checker.
But (you knew there had to be a “but”), first and foremost, the 1.1 version of the application is unreliable, and bonks on way too many PDFs. Reported errors are generally the always-informative “unhandled exception”, with the close runner-up being “An error occurred because of unsupported elements.”
Both of these errors occur far too often – as a result, the PAC just isn’t a production accessibility tool – yet. The developers do invite users to send them files that break the software – and I’ll add my encouragement to theirs!
Just like Acrobat, PAC reports a lot of “false positive” errors, including misinterpreting artifacts as content lacking tags. On the other hand, that’s one of a very few advantages (apart from reliability!) Acrobat retains over this excellent free software.
The following table compares features of Acrobat’s Accessibility Checker (version 9.x) to the PAC 1.1.
| Feature | Adobe Systems Acrobat Accessibility Checker |
Accessibility for All PAC 1.1 |
Advantage |
|---|---|---|---|
| Reliability | The standard by which others are judged | Poor (for now) | Acrobat |
| Check for document title | No | Yes | PAC |
| Check for bookmarks | No | Yes | PAC |
| Facilitate check of logical reading order | No | Yes Use the Preview function to confirm that the logical reading order is correct. |
PAC |
| Check for the use of section heading tags | No | Yes PAC reports errors if a document doesn’t contain any heading tags at all, or starts with an H2 or H3 instead of an H1. |
PAC |
| Check for sufficient contrast in page content | No | Yes | PAC |
| Check for incorrect tag structures | No | Some PAC doesn’t report non-standard tags and reports errors on standard tag types such as <LBody>. |
PAC (with errors) |
| Detect unmarked (untagged) content | Yes | Yes, see note PAC reports some items as untagged content. |
Acrobat |
| Check for language setting | Yes | Yes Tags show language attributes in the Preview! |
PAC |
| Check for correct character encoding | Yes | Yes | PAC |
| Validate list and table structure | Yes (with errors) Acrobat catches a few common errors in table and list tag structures, but ignores others. |
Yes (via Preview) PAC doesn’t report errors occurring in many common table and lists, but “nesting”, structure errors are readily visible via the “Preview” |
PAC |
| Check alt. text for images | Yes | Yes (via Preview) | PAC |
| Check for form fields with no tooltips | Yes | Yes | PAC |
The PAC won’t find all the accessibility problems in your PDF, and it can’t fix the problems it does find. But it can really help PDF taggers do their jobs. Most importantly, the PAC really helps in visualizing the significance of tagging for accessibility – and thus, in highlighting how critical even “small” errors can damage the reading experience.
Sure, some of the interface includes misspellings and other detritus of early-stage software developed by those for whom English is a second language.
Here’s hoping that the PAC will focus the minds of the commercially-minded, and inspire new implementations addressing the challenge of PDF accessibility. In the meantime, collect some good Karma by donating a few dollars to help these good folks continue to do their thing!
SYSTEM REQUIREMENTS: PAC is Windows software, and requires Windows XP or later along with the .NET Framework 2.0 SP2, Adobe Reader 8 or later, plus current versions of either Firefox, Internet Explorer or Google Chrome.