Maybe not the help you're looking for but I would personally open it in a vector program (illustrator, corel draw) scale it by using the diameter of the button holes. Trace it with the pen tool. Export it as an autocad file DWG. Open it in google sketchup and make sure you have the units right and use the measurement tools to get exact dimensions. Of course if I had autocad I could do it from there but sketchup is free.