Why won't iTunes let me manually sync PDFs to iBooks? I have my iPad set to manually manage content (i.e. drag and drop, not sync). I'm trying to add some PDFs to iBooks, but it refuses to let me copy them to my iPad. I can do this with epub books just fine. Is this a known limitation in iTunes, or a bug?

Is there any workaround (to clarify: still using iTunes) that doesn't involve having to use the sync option (which forces me to sync videos as well, which is not workable)?
You can get the PDF's on your iPad via some other method (e.g. Email, DropBox, etc.) and then choose to open the PDF inside iBooks.