When the PDF became a standardized format in 2008,it served as the backbone for other PDF subset standards that mainstreamed certain uses of the PDF. Examples include the PDF/X (professional printing and publishing), the PDF/A (digital archiving) and soon, the PDF/UA (Universal Accessibility).  

The new subset standard,PDF for Universal Access (PDF/UA) is slowly, but surely, going through the standardization ranks. The PDF/UA subset standard may still be relatively unknown right now, but people will know about it soon enough.