While printing an InDesign document as a PostScript file, the options to customize page are disabled.
This issue occurs if you have selected Device Independent as the PPD. Select Adobe PDF from the PPD list to resolve this issue.
If Adobe PDF is not listed under PPD, follow the steps below to have Adobe PDF as an option in the PPD list. The Acrobat 9 PPD supports custom page sizes, which are often necessary when using this workflow with the Print Booklet feature in InDesign.