Banner Pocket will help you get the printed sheets arranged in the way you need for attaching the front and back side pockets together. It will crop one side's banner to leave blank space available for the glue or sewing. Those areas that have been cropped away are instead printed on the other sheet so that when you fold that sheet over the other the image line up.
This is done in a fully automated way for banner files with one or two pages. If the file only has one page, that page will be printed on both sides and arranged properly. You can set the values for the banner size and how large the top and bottom pockets should be.
There is also a mode for single-side prints where you get the fold marks.