I've never taken PCAT. but from what I've heard, you are given the erasable notepad. I think you can write down anything once you are situated in front of the computer. Maybe during the long break, take a peek at all the reference notes. Sit down bit earlier without starting the test and write stuff down. Then don't erase it until math section comes up. I don't think there is any rule against it.
Anyone please confirm if you have taken the PCAT.