When posting documents to the web, Google Docs are arguably the most accessible to persons with disabilities. Additionally, Google docs are more readily translatable into other languages.
The most common document type, however, is still PDF.
sample PDF text that is selectable is also readable by most screen readers.
PDFs created from scans too often are not accessible. If you can click-drag and highlight text within a PDF, then it probably is already accessible, as in this case.
What to do when your PDFs are NOT compliant

What to do when your PDFs are NOT compliant

Open the PDF in Adobe Acrobat PRO. Don't have PRO? See the Director of Instructional Technology.
Open Tools > Text Recognition.
Accept the defaults and perform the conversion on the current document or select an entire folder of documents.
The resulting files should pass the previous test.