[Gimp-user] Adding color to file

[sl60 <forums gimpusers com>]

I want to color parts of what has been sent to me as a black-and-white pdf (line
drawing, basically). What I usually do in a case like this is to change the
original layer to Multiply, then duplicate this and multiply again. Then I
select each part of the drawing I want to color and bucket fill it (different
colors for each). if I save this as a pdf and open it, all it shows is the
colors without the line drawing. if I save it as a png, all is preserved.

My question is--should I save the pdf as a png or jpeg first before I start the
entire process? It's a very low resolution drawing. Or does it matter? It's a
big file (the original is on a 24"x36" sheet and it will probably be printed out
at some point).

I thank you for your help in advance!

-- 
sl60 (via www.gimpusers.com/forums)