The problem with pdf files is that you never know...

Some files convert to a usable (I'll qualify that in a moment) form, others
are convertible, but may have unreadable sections or other serious problems
when used with screen readers, and many, because they are scanned in as
pure images, are totally useless.

Usually documents from a particular source are reasonably consistent, but
that can depend heavily on the kind of source it is -- for example,
libraries typically have a lot of documents and archival materials that
come from various sources and thus retain little control themselves on how
the documents are prepared.  The ACM digital library is an example of a
fairly consistent document format, and one, which despite a few annoying
little problems, is mostly "usable".

Even under the best of conditions, when the documents are converted to
text, you usually end up losing formatting like paragraph breaks and such,
and lines can be broken in strange places with hard hyphens, etc.  Thus,
you can read the document, but it can sound choppy and be difficult to
navigate and review.  I have had documents that converted to having
hundreds of lines with one, two, or three words onthem, and while all the
material was there, it was a real pain to work with.

Also, if you are crossing platforms, and the fonts aren't in sync, or the
document was saved without font information, then certain characters such
as ligatures typically won't translate, making words that contain those
characters unintelligible and disruptive to continous reading.  This often
happens when somebody prepares a document on a Mac and I am trying to use
it on my PC on the other end.

There is also a security flag in some files that the author sets so that
the document can't be converted, but mostly I have found that when this is
the case, I can bring the document up in Acrobat and cut-and-paste the text
into another file.

So, while some documents are usable, there are always formatting problems
to deal with and you are never quite getting the same thing as the printed
version, and besides that, it is always extra steps and more inconvenience
than one really should have to go through to access a document, especially
if you have to mail a huge file to the conversion server over a dial-up
connection.

I don't know how far the new MSAA-enabled Acrobat will get us in the
future, but there is always the huge legacy problem to contend with.  There
is a lot of work to still be done to make this portable format truly
portable and accessible.

-- Jim

------------------------------
James A. Rebman

Cognitive Levers Project
Center for Life-Long Learning and Design
Department of Computer Science
University of Colorado, Boulder

"In times of change, the learners will inherit the earth while the learned
will find themselves beautifully equipped for a world that no longer exists."

- Eric Hoffer