[dmlorenzetti]

As a similar, but easier, experiment, try listening to Adobe Acrobat read a PDF file out loud-- especially if the PDF contains anything at all interesting, like mathematics, figures, tables, or any kind of "float" that pegs to the top of a page as the text flows around it.

While tools are available to let the PDF creator tag the document in order to facilitate reading, in practice they don't seem to be used much, and even then the experience is painful at best.