If you're using Assembler, which comes with LiveCycle PDFG, chances are you're already familiar with http://help.adobe.com/en_US/livecycle/9.0/ddxRef.pdf.
Here's a simple DDX for removing a page (or pages) from a pdf:
<?xml version="1.0" encoding="UTF-8"?>
<PDF source="inDoc" pages="1,3-last"/>
You'll notice that you have to specify all of the pages that you want to keep, and in this scenario we deleted page two.