iBooks continually deletes my PDFs (and EPUBs not purchased through Apple) from my device. They’re still available to redownload from icloud (even files that I specifically did not upload to the cloud, to prevent this problem), but I’d love not to have to download my own files every third time I need them.
It seems to be a bug. I know how frustrating it is, and sadly this hasn't been addressed on the iOS 11.1 betas (at least for now).
It appears to happen only with books not bought through iTunes and PDF's and, when your device is running out of space (For me when my iPhone had less than 10Gb's of local space, which btw is a lot of storage left for iBooks to start deleting local-stored books).
You can try for now increasing your available local storage, uninstalling or deleting the app and files hasn't worked for me, but give it a try.
Everyone having this issue please report it to Apple so they can fix it, http://www.apple.com/feedback/
Weird. I just checked again and all of my books (which is many 100's and I think about 4 gb space) are stable and not playing the "now it's here, now it's not" game. That's been for a least a week and it was completely reliable in removing them within hours prior.
That said, the space under "iPad Storage" says I have about 40gb free (when it used to say I had about 5!) and looking at per application space, it says iBooks is taking about 39.2mb (when it used to read 4 gb in iOS 10.x)!
They've done something weird with the storage. Not sure why I'm lucky enough to be stable, but it's definitely not doing what it was doing before for me. That said at one point I totally deleted and reinstalled iBooks )(though after that it was still broken_. Maybe that reset interacted with later versions to make it stable. It's been fixed for me since about 11.1 beta 2 (I meant to post it here earlier, but couldn't find the old email links).
Anyway, I'm about to go to 11.2 beta - we'll see if it changes anything. BTW anyone can join the beta program:
I've generally found it has been safe, but caveat emptor, your mileage may vary.
Can I stop iBooks from removing my PDFs from my device?
