No limit as far as I am aware, just remember that you can't have pencil written notes in any of your binders or books. The proctors will think you are transcribing the exam and planning to sell it. If you already have pencil written notes for your binders, photocopy them. If you have pencil written notes in a book, redo them in pen or put clear tape over them so you can prove they were not written during the exam.