For any webmaster or content manager, PDF files are a mixed blessing. They are an easy fix to the problem created by a content author who brings in a document that has to be published online "right now." But PDF files are a nuisance to many content browsers who want to quickly determine if a document has the information they need and they can be an absolute barrier to users with alternative display devices such as screenreaders and handheld displays.
Here is an entry point (probably one of many) for learning about making PDF files accessible: Planet PDF - Learning Centers - Accessible PDF http://www.planetpdf.com/learningcenter.asp?ContainerID=1505
Here's an interesting article, from a UK developers site, about an online service that prepares PDF files that are more suitable for screen-readers:
http://www.theregister.co.uk/2004/07/11/pdf_tags_blind/
There are more interesting Accessibility links to explore at the end of this article.
The aDesigner is a disability simulator that helps Web designers ensure that their pages are accessible and usable by the visually impaired.
Go to: http://www.alphaworks.ibm.com/tech/adesigner