Below are guides from NCDAE(link is external) on how to create accessible versions of PDF files.
- Creating Accessible PDF Documents In Adobe Acrobat X(link is external)
- Creating Accessible PDF Documents In Adobe Acrobat XI(link is external)
Note: Prior to creating the accessible version of the PDF file, first use Adobe Acrobat's OCR Text Recognition(link is external) feature to covert the document that is accessible to screen readers if it is not yet already in text format.