Your PDF creation driver is generally installed as if it was a printer driver. To set it up for a custom page size you must go into the Printers & Faxes menu.
From the operating system desktop, select Start==>Control Panel:
Depending on your type of control panel display you will need one or two clicks to get to the Printers and Faxes window:
Select "Printers and Faxes:"
Click once on the name of your PDF creation driver to highlight it. Then, with the driver highlighted click on the File menu in the upper left corner of the window and choose "Server Properties:"
Select the "Forms" tab, check the box that says "Create a New Form," give that form an appropriate name in the "Form Description" box (like "Lulu book" or "6x9") and put the width and height in the boxes. Select "Save Form" and OK your way out.
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