This advertising concept from Arc Worldwide Advertising was developed for the Malaysian based NGO Treat Every Environment Special (or TrEES). The idea is to place this sticker on the glass of your companies copy machine so every page that is copied is marked with a little reminder in the margin PLEASE USE BOTH SIDES AND RECYCLE AFTER www.trees.org.my.
As long as the documents you copy don't need to be free from extraneous marks this could be a good reminder. It would also serve the dual purpose of distinguishing between a copy and the original. Now these aren't for sale, but it would not be too hard to make your own. All you need is some scotch tape, a marker and the ability to write backwards.
Source: Ads of the World