The programme is Windows Publisher 2007 and the files are envelopes which
have all been originally compiled on the old printer.
What about removing the old printer, even temporarily, and printing
each of the documents once? Since the old printer won't be available,
Pub will either have to use the new default printer or it will pop up
a dialog asking which printer to use, right? From what you're saying,
once you get it to print with the new printer, the files will be
automagically updated to reflect the new printer.
The only part that confuses me is that I have a lot of MS Pub files
here, and no matter what, when I try to print any of them, I can
easily specify which printer to use. I don't know why you can't do the
same. It's almost like you're using the Print button on the toolbar
rather than the Print command in the File menu.