Where are my Play Books pdf files?

[Telemachus]

I have several dozen pdf files I downloaded free from Google Books via Play Books on my Samsung Galaxy S6 Edge+.  I know these files should be on my phone, because when I used Play Books to download them, I saw the download message for each one on my phone, and when I open Play Books and go to My Library, hit All Books, and from the Options menu hit Downloaded Only, I see these books, each of them having the underscored checkmark indicating they have been downloaded, and if I hit the three dots, one of the options is Remove From Download.  So all of that indicates the books as pdf files must have been downloaded on my phone.  And I can read them fine on the phone via Play Store.

My question is: where are these files?  I might want direct access to them to rename them or to use a file manager or another reader to arrange them in folders (something most unfortunately and puzzlingly Play Store doesn't let you do.) But I can't find these pdf files anywhere.  I've looked and looked using My Files, sdcard, and ES File Explorer, looking in all directories and subdirectories, and I can't find them.

Does anyone know where Android puts these Play Books pdf files?  Or does anyone know of a way to search for all pdf files on the device? (ED File Explorer has a search function, but when I use it to search "pdf" it finds only a few stray files which aren't the ones I downloaded with Play Store.) Thanks for any advice.

[SuzyQ]

This Q&A exchange on StackExchange may help - it doesn't give a definitive answer, but it may give you some alternatives (such as "enable upload", upload to your Google account and work with the files from there).

storage - Where does Google Play store its ebooks on an Android device? - Android Enthusiasts Stack ...

[Telemachus]

Thanks I'll check it out.