I contacted support and they told me that restoring notes and highlights is no longer supported for emailed docs... that sounds weird to me because I haven't seen anyone else mention it. Saving the reading progress is supposed to work but on my device it still doesn't after updating to 5.8.1. Someone is supposed to get back to me in about 24 hours. I'd be pretty pissed if after going through all the trouble upgrading I don't get my notes and highlights back
I also hope I can downgrade from 5.8.1 easily too.