PCB designing is Printed Circuit Board design, in which the electrical cicuits are drawn virtually over a software. The software i use for these designs is proteus. Cross-platform -- EAGLE can run on anything: Windows, Mac, even Linux. This is a feature not too many other PCB design softwares can boast. ... Free/Low-Cost -- The freeware version of EAGLE provides enough utility to design almost any PCB in the SparkFun catalog.