Seriously? If someone asks for vietnamese support (for example diacritics stacking) you will tell him “chat with pdfs because all we care is ascii” ?
If we talk about the blind there is a new software called latex2nemeth (which I codeveloped) and which is standard in TeXLive, MikTeX and MacTeX installations. It goes directly from LaTeX to Braille with minimal editing of the LaTeX file. For math it supports Nemeth which is the standard notation for math for the blind in many countries including US. So for such applications the choice of PDF is wrong.
You may say “screenreaders?” This is again wrong choice as long as we talk about Math. You can not read a math document to a blind person and expect him/her to follow. It will not work. Unless we talk about primary school level.
Currently other solutions (libluis for LibreOffice docs, Duxbury for Word and others) fail badly on LaTeX files, at least at the college level Math.
The software (GPL3) was developed for a blind student that insisted to enter the Math department (usually people avoid it because there was no way to have books to read in braille) and she just graduated using latex2nemeth. The first blind Mathematician in Greece after about 60 years.