I had several PDF files in iTunes that I had added authors to. Then I upgraded to Mavericks and launched iBooks. It moved my books and PDFs from iTunes, but many of my PDFs now show the author as "Unknown Author".
Is there a way to add an author to these files? I cannot "Get Info" on the file in iBooks like I used to be able to do in iTunes.
Note: This question was originally asked about OS X 10.9 Mavericks. Now that 10.10 Yosemite is available, there is a way to do this easily in iBooks.
Best Answer
You can use the Automator workflows. Choosing PDF on the left and then dragging the action "Set PDF metadata" (or something similar, my version is in Italian) on the right part of the Automator window you can put author, title and whatever in one or multiple PDF files.
Issues and workarounds: if you update the metadata directly on your PDFs in the iBooks folder it will not update iBooks, so you won't see any change. I suggest to copy your PDFs on you desktop, erase the PDFs from iBooks, use Automator to add the metadata and then re-import (drag and drop is useful here) the books in your iBooks.
I have just finished updating my files, you can't go wrong ;)