Are you not using any of the software formats listed here? (TARGET, EAGLE, PROTEL, ORCAD, UltiBOARD, PROTEUS, SPRINT, QUICK-ROUTE, EASY-PC, EDWin, PCAD)
Would you still like to save yourself the cost involved in editing gerber and drill data?
It's easy: simply load your gerber and drill data into the gerber viewer software GC-Prevue.
GC-Prevue is available free of charge and can be downloaded from here
We will be happy to answer any questions you may have regarding GC-Prevue!