I was asked how to save a DWG file (Autocad) in PDF format and change all of
the line colors to black.
When printing to the default PDF printer, you have the option of adjusting
the pens. Globally set all pens to color number 7 which is white. If the
background default is white, then this will print as a black line.
You do not have to manually change all of the screen colors - just set each
pen to number 7.