I don’t think making the file a PDF format would be a problem at for the visually impaired. As someone who is visually impaired, I can honestly tell you that there are now programs available paid or free that can read PDF format.
Just to give an example, the Adobe Acrobat Reader already has a Read Out Loud feature. Located at the view tag, then by selecting Read Out Loud at the very bottom. If they don’t like the voice or they want to adjust something they just need to go to the Edit tag then select preferences. They’ll view the categories, they must select Reading and that is where they can adjust the Read Out Loud to however they’d like it.
The only down side that I can tell, is if you put pictures, the text reader won’t pick that up. Even with flavored text, I mean text with designs on them, as long as the letters are readable the text reader will be able to read them.