Not much I guess. It seems to be in terrible condition and there doesn't seem to be anything that makes it stand out like autographs or rarity, but I could be wrong. It might still be worth something because of it's age though, not much, but something.
Btw this thread just reminded me of pawn stars, love that show
Edit: I did some research and found this. It looks just like your poster. It seems to be a poster that came with the vinyl soundtrack back in 1977. More info here.
It's actually in a lot better shape, it's just that I had poor lighting and I took the picture with my iPad's camera, so the picture makes it look a lot worse than it actually is, but thanks for the info.
Consumer posters aren't worth much to collectors especially ones damaged (yes the folds are damaged). Saw the same poster in similar condition on ebay for $10.
This one seems to be a 1977 (original star wars release) poster.