Getting the Mac to read PDF files aloud I tried previous suggestion to have my MacBook to read PDFs with speech. I tried Edit -> start speaking in Preview. I also tried the regular way of of using a shortcut key preset in System Preferences for a highlighted section. Nothing happens. 

I checked to make sure it reads using other documents and/or screen text. 

My eyes need a break and I would like to get speech to read aloud the PDFs. What other suggestions do you have?
Preview voice reading will happen after selecting the text you require to be read first / as mentioned above it needs to be selectable and recognisable text - then proceed with previous steps: Edit -> Speech -> Start Reading

Hope this helps