While generating assembly drawings for a recent PCB, I wanted to printout the silkscreen layer at 2x scale.  The image was in an eps and the following almost did the trick:

pstops 1:0@2.0 silk.eps silk2.eps

However, the bounding box wasn't updated with the scale.  Hand-editing the header of the output file from:

%!PS-Adobe-3.0 EPSF-3.0
%%BoundingBox: 0 0 217 217;
%%Pages: 1

to:

%!PS-Adobe-3.0 EPSF-3.0
%%BoundingBox: 0 0 434 434
%%Pages: 1

did the trick nicely.