I meant also to ask about your position on accessibility compliance with respect to Section 508
(http://www.section508.gov). Does PDFTron have anything official to share?
PDFTron SDKs provide all the APIs and tools that could be used to meet various accessibility guidelines. For example, some of our customers (e.g. jabbla) use PDFNet to implement PDF viewers and document processing apps specially designed for blind or visually impaired.
PDFNet & WebViewer can also be used to extract text and for alternate content representations, however it is usually your own app that determines what options will be exposed to the user.
PDFNet also can be used to create or edit files that are compatible with PDF/UA.