JAWS Access of PDF: A Users Guide - Guidance and technical advice for screen reader users from the RNIB. - http://www.rnib.org.uk/xpedio/groups/public/documents/PublicWebsite/public_accessingpdf.hcsp
RNIB Media Briefing on Accessible PDFs - Personal notes and recollections by isolani, from an briefing by the Royal National Institute for the Blind. - http://www.isolani.co.uk/blog/access/RnibAccessiblePdfMediaBriefing
WebAIM: PDF Accessibility - In depth article considering both the creation and reading side. Includes discussion of using HTML as an alternative, understanding PDF tags, and dealing with existing untagged files. - http://www.webaim.org/techniques/acrobat/
Web Usability: PDF and Accessibility - Overview article, including discussion of how to create accessible PDFs, and possible alternative formats. - http://www.usability.com.au/resources/pdf.cfm
Planet PDF: Accessible PDF - A collection of articles covering accessibility and related issues in PDF files. - http://www.planetpdf.com/enterprise/learningcenter.asp?ContainerID=1505
AlastairC: The Four Levels of PDF Accessibility - Blog entry describing different degrees of accessibility, how to achieve them, and the implications for content producers. - http://alastairc.ac/2006/07/the-four-levels-of-pdf-accessibility/
Adobe Accessibility: Read PDF Content - Official information about the accessibility feature built into Adobe Reader and the PDF format. - http://www.adobe.com/enterprise/accessibility/readcontent.html