Does anyone know how to best fit a surface to a surface. I know you can best fit a cloud to a surface in Digitized Shape Editor but haven't found a way to best fit to similar surfaces together.
That isn't really a core competency of CATIA. You could try putting a bunch of points onto one of the surfaces and then fitting that cloud to the other surface, then offset the first surface the same amount. There is other software that is better at this, try looking into Spatial Analyzer or PolyWorks.