Starting Graphic File format

I am using IsoDraw 7.3 to create TIF and CGM files for use in our manuals. I receive many different starting graphics to build on in IsoDraw adding leader lines, notes and everything else. What do you all think is the best file format for the incoming graphic? I am trying to maintain the best resolution I can with a final file size for TIF files under one MB. Typically the final file goes into Arbortext for manual creation.

Thanks

Keith