Ok when you open pepakura, pick your file, say the left thigh. since you should have the unfolded models I linked earlier, you can click on "2d pattern window" and then "Scale Up/Down development by specifying value" and then you should see a new window pop up. Mine says "Assembled Size (height) 36.0 cm" which is =my= size. since you're a bit taller, you're going to need to change it.
1. get a tape measure. a tailor's tape measure is best, but you can use a hardware tape measure too.
2. look at the Valve HL2 image i posted earlier to see where the piece sits on G.F.'s body, in our example the thigh goes from right above the knee joint to almost the waist.
3. measure on your body that same distance. as i said earlier, from just above my knee to just below my waist (i used where my hip curved back in) is about 36 cm.
4. input your measurement into pepakura. the whole model will jump up in size.
5. reposition the pieces on the page. since you're going up in size, you'll have to move the pieces around. possibly even make them sit on two pages. just work with it and you'll be fine
Hope that helps you man.
Also, I'm going to put the unfolded heights next to all my posted models so people can reference them easier.
Also, also: I'll post up some pictures of me wearing the stuff I can wear without cutting it open (which I'm going to wait to do until I have $$$ for resin and fiberglass) so you all can see the scaling.