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Re: PDF/A accessibility

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From: Duff Johnson
Date: Aug 10, 2011 12:03PM

All,

Karen McCall has pointed out to me that confusion on the question of PDF "reading order" may be due in part to my failure to use a term that may be more familiar to the AT community: "raw print stream".

So... in brief, here's a translation of PDF terms - I hope this clarifies things....

"reading order" = the raw print-stream (interesting for rendering)

"logical reading order" = the sequence (and nesting) of PDF tags (interesting for accessibility)

In the absence of tags (or software capable of reading tags), AT users are typically stuck with the raw print stream, which (naturally) leaves them unimpressed (at best) or utterly frustrated (the typical case).

The solution:

1) The software used to consume PDFs (both the PDF reading software itself and the AT) must understand PDF tags.

2) The PDF in question must be tagged correctly, just as images must have alt. text, tables must include valid table structure, etc, etc.

I hope this helps.

Duff Johnson

US Committee for ISO/DIS 14289 (PDF/UA), Chair

p +1.617.283.4226
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On Aug 10, 2011, at 8:29 AM, Humbert, Joseph A wrote:

> I have to say that after reading your article that it seems to mislead the audience. The article makes many correct statements concerning PDF accessibility, except for:
>
> "And that's why we can safely and responsibly ignore reading order when considering accessibility in PDF."
>
> It is true that if a PDF is tagged correctly and the software used to consume can read the tags then the "logical reading order" will be correct, but as you even point out it prior emails, "'logical reading order' is the concept of interest". Therefore, some type of reading order, "logical" in this case, is very important. For many users of assistive technology (AT), the order in which the AT software reads the content is how the user perceives the logical reading order. Headings and other tags help to improve a user's understanding of logical reading order and allow advanced users to navigate the document in their own "logical" reading order, but never the less reading order IS important.
>
> Please don't get me wrong, the articles message about tagging PDF files and using software that supports creating accessible PDFs is wonderful. You seem to be well versed in accessibility issues. My interpretation of Ron's point is that "reading order" in some form is important. I may interject that I believe Ron's comments come from the point of view that many programs which create PDF/A documents do not automatically tag the document correctly, thus creating inaccessible PDFs.
>
> "Pagination" is also extremely important, particularly when a textbook or print article is being converted to a PDF. When this happens, my opinion is that the original "pagination" of the book/article should be preserved. Ron, I'm not sure of your complaint with the PDF/A or PDF/UA specification is in terms of "pagination" so you will have to comment further.
>
> Back to the original question of the post, it seems as though the PDF/A specification does not have any accessibility limitations included in the specification. I have not read the full PDF/A specification so I cannot be 100% sure. Unfortunately, the software used to implement the specification in creation of a PDF/A file may produce accessibility issues that may have to be addressed manually.
>
> Please forgive me if I have misinterpreted something.
>
> Joe Humbert, Assistive Technology and Web Accessibility Specialist
> UITS Adaptive Technology and Accessibility Centers
> Indiana University, Indianapolis and Bloomington
> 535 W Michigan St. IT214 E
> Indianapolis, IN 46202
> Office Phone: (317) 274-4378
> Cell Phone: (317) 644-6824
> <EMAIL REMOVED>
> http://iuadapts.Indiana.edu/
>