Bulk mail inde

When I do a data merge on WORD or PAGES with #10 envelopes to print out a series of envelopes, it cuts off the type on the most right hand side, in this case the ''bulk mailing'' stamp-like-thing on the upper right hand corner. When I had a PC, I was able to somehow manipulate it into thinking it was printing on bigger paper. But on my MAC, I can't shrink it to make it fit nor can I find a way to manipulate it. I have it set on #10 envelopes in page setup, so what am I doing wrong? this is a problem that I have had for years. There has to be a simple solution.