Undo iCloud backup?

I made a mistake and backed up my iBooks and PDFs to iCloud/iCloud Drive (I don’t know the difference) and so they’re in there but every time I turn off iCloud, the books disappear. How do I go back to just having iCloud backup for books turned off and having the books just sitting there always downloaded on the device? When I go back into the app every time I have to redownload all of the documents which is annoying and I can’t see them offline like I used to.