The problem with printing a second invoice on the page is that if the second invoice is long, it will be spread over parts of two pages. However, if that's the way you really want to handle it, here are a couple of things you can look at.
1. Turn off "New Page After" for any invoice footer section.
2. Turn off "Keep Group Together" for the invoice group.
3. Narrow down or eliminate the whitespace between the groups - headers, footers, etc. - and in the page header and footer.
-Dell