Photocopy all your documentation e.g. passports, travel documents etc in case your handbag is stolen or lost etc. It is much easier to replace if you have a copy.
Buy yourself a travel journal - it is fun to read about your adventures when you return home. My travel journey has stubs from museumsI have visited, drawings of quilts which took my fancy etc.
Batteries for your camera - buy yourself a spare - learnt this lesson the hard way. One battery can be charging whilst you are happy clicking during the day.
Nothing to do with paperwork but whilst I think of it - buy yourself a pack of earplugs. You may not snore but your roommate might! On the plane (even in cattle crush class - economy) you will be given a toiletries bag with toothpaste, toothbrush etc as well an eye mask. The eye mask is great for use in your hotel room.