PDF/UA is the ISO standard, ISO 14289-1 published in 2012, that provides a set of guidelines for producing universally accessible PDF documents as well as specifications for compliant assistive technology (such as screen readers, screen magnifiers, or joysticks) and PDF reading software. If the PDF/UA technical and semantic requirements are followed, universally accessible files can be created so that persons with disabilities can navigate and read their electronic content.
See PDF/UA for more information.