after reading the post, i'm assuming that the sheet was set up to have two postcards landscape and three postcards portrait (or vice versa) to fit on the sheet. there is a solution but its massively convoluted and complicated involving excel, acrobat, bridge and indesign. in layman's terms it involves taking the merged single-page pdf and splitting it into individual files renamed in bridge to have filenames of 001.pdf, 002.pdf, etc. from there, a datamerge file has to be made in excel with card1, card2, card3, card4, card5 header and then the 001.pdf 002.pdf etc underneath. once that's done, make ANOTHER merge file but make it merge into how you want the template imposed.
i was going to write the steps out but it was two pages long! i hope you can understand the gist of what i've written.
its not something that can easily be done in a cheaper imposition program as they don't tend to do ganging like this. more expensive software like dynastrip or preps will do it easily but those programs cost thousands of dollars and are print industry standard, and not necessarily a solution for this particular issue.
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