What i do...
Take your printed patterns and a pen with a very small tip (nothing too small like a tack)
Place your sheet on the foam, DO NOT CUT OUT THE PATTERNS
Take the pen and punch a hole in the paper at every corner on a pattern and every midpoint between them.
Lift off your paper and connect the dots!
Also if you have a Laser Printer, take your printed sheets and set them pattern side down on the foam, then rub acetone on the back of the paper with a papertowel. lift and the ink should have transferred to the foam