BAckground file for engraving


Hi I try to load a file for the background when I want to do engraving. But the file after loaded is not to the scale. Please advice. What is the dimension of the file and resolution etc in order for me to load it in as background. In this case, I can have different engraving design on a same product. Loading background for engraving so that I know where to place the design I want to engrave onto my product and not engraving the shape of the product onto the product. Anyone face the same issue? Please advice.