In Pepakura 3 its under 2D Menu, go down to scale, and click adjust scale. On The flying squirrel helm, I had to increase by 10%, the original scale just was too small for my head and for that of most of my friends as well. I even tried at 107% and it was still too small. The scaling depends upon the original size the part was built on. Sometimes it is scaled to John-117 (master chief) and sometimes to the modeler. It works best to find whichever size is the determining factor, measure yourself and use that. For me and my melon head, i had to jump up the 10% just so I could get my head inside the darn thing. But it all depends on you. It doesn't hurt to make the helm a couple times either, you learn and get a nicer result the 2nd and 3rd+ times around.