Any way to subtract one Gerber from another?

[paulvdh]

KiCad can re-create a PCB from any set of Gerber files (provided it’s not in an ancient and obscure gerber dialect, gerber history is obscure). For more info:

Reverse engineering KiCad project from Gerber files

The goal of this reverse-engineering tutorial is to re-create a complete KiCad project from partial information assuming the only information available is a schematic in some readable, (but not EDA form, such as a .pdf or a .png picture), and a set of gerber files. The Gerber files will create a PCB with much PCB information missing, however, using this method is easier than re-designing a PCB from scratch, and can also be extended to any other program that creates Gerber files. What is “resc…

I created that topic some years ago. These days you can also import an image (taken from a PDF) into the schematic editor and place symbols and wires on top of it. It’s not perfect, but it is a significant help for reverse engineering and re-creating a project.