There should be a
folder in the zipfile you download that says foam. Those are the pepakura files you want to work with. When you print out make sure in the settings tab for pepakura your paper size is what you want to print out on. Usually it's defaulted it A4. Then as long as your pieces are in the page borders with like 1/4inch of tolerance around the border everything should print out fine. When you want to scale the parts use 2D Menu and select scale and play around with that.