Hi Federico,
From my last message, I went ahead and optimized the reader code that seems to have been written by someone with not much experience in Apple system frameworks (nothing wrong after all. Nobody was born with knowledge...).
For example I removed the timers that were used to force the update of the page and thumbnails and other sparse things.
I have already added the code to generate all the page previews asynchronously to be used for the thumbnails.
Also by iterating all the pages to make the preview I get a complete PDF that can be stored and used without reloading it from the network next time (if it stays the same).
I think the thumbnails and the PDF should be saved locally by the core library as that is a core functionality...
Once I've done with the thumbnails, I will test is the annotations and multimedia stuff works well.
Luca Severini