Using this method which is using the app called Ez Pub Creator
http://futurejones.com/easyepub/tuto...-highlighting/
or
the Elisabeth Castro tutorial on Read Aloud pubs. If you are not familiar with it, they are both very similar but the Ez Pub Method uses the read aloud voice from the mac where the Elizabeth Castro tute uses an audio file supplied with a voiceover. The EC book method also uses SMIL files.
Hope this helps with your answer.
Plz advize
RD