Hi Maggy,
This is a feature people wanted for a long time but it never came. An alternative is to use voice over but it doesn't really allow you to read out loud the highlighted text, it has to be the entire document.
There is one other way. You can save the entire document as txt file and open it with any browser of yours, tested on chrome or safari. Select all and right click, then "add to itunes as spoken track." It will take a few minutes and then you will have an audio file you can play. Press pause key on the keyboard to pause or resume while reading.
What you want is Capti, Ghost reader, or Kurzweil.
Capti is free, so it's probably the best (especially since it is pretty good quality). It highlights, pauses, etc. And you can export to your phone. Unlike with mp3's or other audio files, it reads it as text, so it doesn't take up tons of space on your phone.
Ghost reader is also good, but costs money and can't export
Kurzweil is a premium software, but honestly I wouldn't invest in it because it's more for dyslexia and learning than just text to speech.
I know voice dream reader might also do what you want, but I've never tested it.
Speechify is close, but the desktop version isn't exactly what you want (it rsvp reads), the phone is.
The only potential downside is that Capti can crash a bit with HUGE documents.
https://apple.stackexchange.com/questions/174578/how-can-you-pause-text-to-speech-so-that-it-restarts-from-where-you-left-off