Steps to take in preparing 508 compliant slides are outlined in a recent AETC ShareSpot, Addressing Accessibility and 508 Compliance. For those not in the know, Section 508 is a federal requirement to make federal agency electronic media accessible to people with disabilities. Doing so requires some pre-planning when preparing documents, including slides.
The ShareSpot article includes a link to a Presenter 508 Compliance Tip Sheet on how to make slides compliant, along with a set of links to other 508 tools. Software packages like PowerPoint have thankfully and vastly improved their built-in tools that make it much easier to develop 508-compliant slides. These tools are preferable to trying to create 508-compliant documents via Adobe Acrobat.