Sync iBooks

I cannot get any of the PDFs I have downloaded to my iBooks on my iPhone 6 to appear on my Macbook Air. They are books I have paid for through third parties, not iTunes, and are protected so I cannot email them to myself. I have also tried connecting my phone to my Mac and gone to iTunes > File > Devices > Transfer Purchases and it still hasn't synced any of my iBooks to my computer. I bought a journal online and want to print it out, but I can't do this unless I can save this file on a USB. Someone please help, I have tried all the other "solutions" on similar questions here to no avail.

Thank you.