An "Accessible" PDF is one that has been Tagged. Tagged PDF makes use of PDF centric markup.
(Starting reference is Section 14 of ISO 32000-1 which the ISO Standard for PDF. The ISO Standard for PDF Universal Accessiblilty, ISO 14289-1, is expected in 2012.)
There is a "quick check" that can be done to see if a PDF is "Tagged".
View the Description tabl of a PDF's Document Properties (Ctrl+D or Cmd+D).
The bottom left has a field "Tagged PDF" which can have a value of "Yes" or "No".
However, this is not "definitive" as one may use Acrobat Pro to set the value to "Yes" for an untagged PDF.
A Tagged PDF may be workable or well-formed.
Workable often means workable for most users of AT most times but, sometimes, lacking due consideration for color contrast or low vision issues.
A well-formed Tagged PDF typically considers these back in the content mastering by the content author/provider.
The "workable" or "well-formed" Tagged PDF starts with the content author/provider when content is mastered.
Without this one can have a Tagged PDF that is unusable.
Properly mastered, the content author/provider must follow-up with requisite post-processing of the Tagged output PDF using Acrobat Pro.
For untagged PDFs Adobe Reader and Acrobat will programmatically provide a "best-guess" tagging when the PDF is accessed by assistive technology software.
A nice feature the very simple PDF content. Not so helpful for more complex content or content that was poorly mastered back in the authoring application.
How well a PDF performs (or does not perform) when under "Accessibility load" is a direct function of what the content author / provider mastered and piped out.
Both Adobe Reader and Acrobat facilitate PDF consumption by those with low vision.
In Preferences, go to the Accessibility category. Document Colors Options are available there (e.g.. High-Contrast color usage).
As well, each supports user zoom and selection of a reflow mode.
But, again, at the end of the day the buck stops with the content author/provided.
No, "choice of fonts" (such as with web pages); this is not an option with PDF.
It is a "PDF" thing not related to applications (see the ISO Standard).
Message was edited by: CtDave
Thank you for trying, but we talk different languages. I am a user, not a
techie. Our definitions of accessibility are far apart. To the user it is
accessible if it overcomes his disability. Your definition only goes as far
as following the guidelines intended to help the disabled. If it doesn't
produce the needed result it is not accessible. Good intentions don't
count. In my case (low contrast sensitivity) the lack of a bold font makes
a pdf file inaccessible. Magnificatin helps very little. At the same time
it may be accessible for others. The viewer decides. The question will
always be "accessible for whom?"
Please do us the favor of going back with my definition in mind and see if
you can answer my carefully written 2nd question. It is the disability to
be helped that is of interest.
I assume that the answer to #3 is "None".
With thanks and best wishes, ===gm===
To answer #3) If you did not create the PDF then you can't decide which fonts are used in it. That's the entire point of PDF files. They need to look exactly the way the creator inteded them to look, everywhere. Of course, this can sometimes come at the cost of accessibility, but there's nothing that can be done about that.
The best option would be to contact the creator of the file and ask them for a version of it in a different font. Explain your condition and hopefully they could help.
Another alternative would be to copy the contents of the file (if this was allowed by the creator) to a word processing application (like Word) and then apply the font settings you prefer there.
"Accessibility" and "Usability" are really two different things.
The former can be (and has been) addressed. Some examples of this are through standards (by standards organizations such as ISO), by recommendations (i.e., WCAG 1.0 and WCAG 2.0), and by identification of best-practices and techniques.
The later is more subjective. For the most part if "Accessibility" is met then, for most folks, most times, there is adequate "Usability".
I realize that this is small comfort when a specific need is not met and this renders content less than usable by some.
As to question #2. I would rephrase it to state: "All PDFs are usable to a certain extent; What is different about one that was made to be accessible? "
What makes a PDF "accessible" is that the content has been properly mastered to support a properly Tagged output PDF.
Thank you but no thanks. For the disabled the difference between
accessibility and usaility is a pedantry too often used as an excuse for
the message being there but being unreadable. When I ask what is the
difference between plain pdf and accessible pdf I want to know about how
they appear to the viewer, not about tabbing etc., the means intended to
make the difference. I want to know the effect seen by the viewer, not the
method. Not a word, please, about the magic, only what the audience sees.