A couple things of note... (maybe they should be added to the tut for clarification)
make sure when you print, that the paper setup is the same as the one on the 2-D layout. A lot of the pep files are Landscape, while the default printer setting is Letter...
If the printer complains about having to scale to make the pieces fit... don't print, something isn't setup right... most likely landscape setting...
You can change the margins to 5mm to allow more pieces to fit per page.
Look at a reference picture as to how far the pieces should go. Measure on yourself. Helmets are a bit tricky depending if you have a large head (like me...). You may have to do a 2 second search on the internet to get inch to cm conversions, then just multiple cm by 10 to get mm.
For forearm pieces you have to leave enough room width wise to allow for the cardstock, fiberglass and any padding you may want to add. Body pieces you will have to measure how wide your widest part is, and how deep (stomach to back without holding your gut in all the way). When you scale the armor pieces, make sure the measurements displayed will actually fit you based on your measurements. For instance if your head is 9 inches wide, and the helmet settings are 9 inches wide... it won't fit... Another thing of note for helmets... if you wear glasses your helmet will have to be slightly larger to allow for them.