If you print your message on a sheet of baking parchment paper, aluminum foil, or some other thin and lightweight material which can survive being warmed up, you might just be able to toss it out the door as is. As long as it’s shaped right, it could make it to the ground intact. In fact, a team of Japanese researchers planned to try this by launching paper airplanes from the ISS. They designed the planes to survive the heat and pressure of reentry, but, sadly, the project never went through.
