What happened was that I was reading one of the PDF files and the next time I opened it, the Book application was frozen. Then, I turn off the ipad. When I turned it on again, I realized that I went from 130 PDF files to 4, losing almost everything. Luckily, around 105 of the PDF files were on my iPhone. Then, I quickly bought more iCloud storage and transferred it there, and then those PDFs now came back to my iPad, but I lost about 25 documents. I would really like to recover them and I do not know which ones I lost.
I tried all kinds of remedies that I found on the web, including one that worked after an IOS update that deleted my PDF files a couple of months ago (there is no IOS update this time):
There have been some other ideas, such as removing the Books application and reinstalling it, which also failed.
Oh, and today my 105 documents became 95.
Very irritating trumpe!
I am quite bearish in a solution, since many people seem to have this problem and have published it with some solutions that worked for them, but none of which worked for me in this cut.
I'm not sure why such a monumental error is so difficult for Apple to handle.
PS: Another thing worth mentioning is that when I downloaded one of the missing PDF files (actually, the one that was frozen), the document ended up in the correct folder of my collection and when I opened it, it was on the page The last time I looked at it, so Book still has some kind of PDF memory, I just hope it can make all the missing PDFs reappear. I'm really scared that I can not trust the Book application, or even iCloud, after all, the 105 documents that became 95 today were theoretically on iCloud!