Several weeks ago I went through a period where I could not get iTunes12.3.3 in El Capitan 10.11.4 to sync newly created pdf's to my iOS9.3 iPad Air. iTunes had no issue seeing older pdfs to sync from iBooks 1.5 on my iMac, it was ANY newly created pdfs, iTunes failed to see them in iBooks. I called AppleCare, the senior tech I wound up talking to watched me on screen as I would make a pdf and then try to sync it. The senior tech had me do various maneuvers and restarts, but iTunes failed to see the newly created pdfs. She had me pull a full system report, and said she would report it to Apple Engineering. Today, the senior tech called back. She says Apple Engineering says to use iCloud Drive instead of syncing w iTunes12. I am to stop using iTunes12 to sync w my devices. Luckily, in the last few days, iTunes has begun to recognize newly created pdf's again. But syncing w iTunes may be on the way to the technology dust bin. In no way do I want to RENT BY THE MONTH to use my computer w any devices. Maybe Apple will force us all into cloud rental.