I'm new to SW and I work with hundreds of similar drawings. I simply want to compare drawings by overlaying one drawing (with the white background transparent) above a second drawing.  I've searched for a function in SW but haven't found one. 

Very primitive methods include:

1. Using a "transparent background" function in Microsoft Paint 
2. Comparing printouts of drawings by holding them up to a window

I've considered making a temporary sheet format and using that as the second drawing layer.  (Would that work in an EPDM system?).

There must be a better way.

Any ideas?