That seems to be a conflict between the iOS PDF viewer and the transparency settings. If you view the document using Acrobat Reader, it should be fine. Still trying to sort out why that happened in the first place, and if this is even the first time. Must confess that I only test the PDFs in Acrobat on a PC, as I'm not a portable device user.
Also, question: has anyone actually received a notification email today from Backerkit that new digital rewards are available? All indications I'm getting are that despite the option being present, no emails are actually being sent.