How do we activate voiceover to read ebooks in Adobe Digital Reader on an ipad

I'm trying to help a visually impaired student who is trying to use voiceover to read ebooks from her university library. she is using an iPad and they only download to be read in Adobe Digital Reader. She has been unable to activate any sort of voiceover function. Is there any help documentation available, or can some please please let us how to get around this issue. Thanks