Why do PDFs disappear from the Books app on iPadOS? I have five magazine issues in PDF format in my Box account. I wished to keep them in my iPad’s Books library and read them there. So for each I did the following.


Opened PDF in the Box app and waited for it to fully download.
Used the sharing action Open in Books.


They all opened in Books and I could page through them. But when I exited the PDFs there, only two of them remained in my library. The other three immediately disappeared from my library.

Why would that happen? Is there anything I can do about it? I can make them available offline and read them in the Box app but I prefer to collect all my reading material in Books.

This happened on an iPad Air 2 running iPadOS 13.3. I doubt this is caused by the Box app; could it be some property of the PDF that causes Books to remove it immediately on closing?
I doubt this is caused by the Box app;


This is highly unlikely. Once the PDF is copied into the Books app, it's not possible for the Box app to remove it from the Books app.


  could it be some property of the PDF that causes Books to remove it immediately on closing?


No.

You can additionally check if you have sufficient storage space available on your iPad. Also, to keep the PDFs into Books app across your devices or between reinstalls of Books app, make sure you have iCloud for Books enabled.