Adding PDF files as Digital Booklets in iTunes 11, OSX 10.9

Hi all,

I've been ploughing through Google search terms looking for an easy fix for this little issue. Simply, running OSX Mavericks and iTunes 11, with iBooks now being in a separate App, I can't find a way to add PDF files to my iTunes library. I have a few digital album booklets that I would really like to put with the respective albums in my library. I can see that you could do it in the past (adding the files, then switching the format to music, etc) but PDFs don't appear in iTunes at all (that I can see, at least) anymore for me to edit the organisation info.

Anyone have any idea? Or am I just being completely stupid?