Once PDF Files are added, Scrivener freezes frequently

I currently participated in the 2013 July Camp NaNoWriMo and I was using the trial version specifically for that, which lasted until august 7th. I had no issues with that trial version, even with adding PDF files (I write stuff out first, so I scan what I write into PDF files and then split the view so I can type it up.) Now that I’ve purchased Scrivener however, I have noticed that since I’ve added more PDF files, the more Scrivener freezes in general. It’s very bothersome. Can anyone help?

Also, it happens when the view is not split between my PDF and the document I’m typing in, but the freezing started to occurr when I started adding more PDF files - that’s when I noticed it, but it may not be the catalyst for the freezing - I have no idea.

Thanks!
Would really appreciate any help.