Where you set the duplexing in your PP7 document, you can choose Long edge or short edge (sometime it says tumble or tumble off).
So long edge is flipping over the sheet on the long edge, so your back page is in the same orientation as your front page, like when you are flipping the page of a book.
Short edge is flipping the sheet on the short edge so the back page is 180 degrees compared to the front page, like when looking at a calendar.
So in your duplexing settings, select short edge or tumble (syntax varies from PPD to PPD) and you will get the expected result.
Hope that help.
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