At my site, I was able to put things on the screen, however the paper isn't see through, and I doubt a white paper would allow see through either. So... the best is to plan for the worst, which is having paper that can't be seen through, and neither can you touch your screen.
Curious thought, at my site, I had a sweatshrit with me, and I need to have that around my waist the whole time, the proctor came in couple times to remind me of doing so. I wasn't cheating or anything, it was just out of habit.
Good luck with the PAT.