I tried that, actually. I had it on my floor with two dining room chairs (on their sides) on it for a whole week after I got it. It didn't seem to help much. It's a thick paper, almost a cardboard. I thought about steaming it in my bathroom, or maybe a low setting with an iron, but I'm afraid the moisture would ruin it. I finally just put it up as it was. I had to wrap the tape all the way around the door because if it wasn't, the poster would roll and lift the tape right off. Ah well... It looks tacky, but it works.
