Q: syncing personal copies of epubs or pdfs across devices

I'm sure this has come up a thousand times, but I've yet to see a clear response. Is it possible to have two-way syncing of personal (unpurchased) copies of books/documents across devices (iOS to Mac and back)? I have seen two methods discussed for DOWNLOADING from one device to another (via iTunes) but haven't heard if this allows for 2-way syncing afterwards. I've also read that by "moving from iTunes to iDrive" you can (in theory) access the files on a different advice: this has not worked for me, and the question of 2-way syncing remains.

My primary goal is to achieve two-way syncing.

Any suggestions appreciated.