What are the advantages of using adobe to the illiterate?

If you are talking about Adobe Acrobat, or PDF, then there really are none, other than if the document was created properly then text-to-speech will work better.  PDF is simply a particular file format  for which a presentation engine exists for (probably) every hardware and operating sytem platform out there.

The point is that it does not matter what presentation engine is behind the scenens. Whether it is Word or QuarkXPress or PowerPoint or whatever: It is just words in front of the eyes.