Creating 508 compliant documents is not just science — it’s a blend of science and art. You can not go to Section508.gov, upload your documents to get some “certificate of compliance”. The only way to test a document is to test the “compliant” document through a screen reader and understand the content. This requires subjective judgement if there is anything besides text; there is compliance and then there is accessibility. Actual accessibility of the document with tables and graphics is dependent on the text description that the document producer uses to augment the graphic or table. If these substitute/alternate descriptions are good, the document will retain as much value as possible.
You can imagine how much variability there could be in a table or chart description- you can add alternate text stating “chart” as a description and pass a mechanical accessibility test, but that wouldn’t make the chart accessible.
The other main component for accessibility is logical reading order. Unfortunately, a document that appears to be in correct order as displayed in Adobe Acrobat may not read in that order. The actual reading order is dependent on the underlying structure of the document, the order of the TAGS and the content CONTAINERS. The tags MUST be in correct order for the document to read in logical order.
Accessibility isn’t complicated- readable text and good descriptions of non-text items, along wih logical reading order are what we are after. More than accessibility, we strive for usability to provide equal value for all users.