What is on page 2? Can the data that continues onto page 3 extend on to page 4? You can print some very complex reports using sub-summaries and grand summaries but this usually requires a lot of time to figure out how to get it to do exactly what you want.
Have you considered splitting the report into multiple layouts and printing the sections you need via scripting?
Edit: Oops. I missed where it said you had already done this in the original post. Or maybe not; you said you have multiple layouts with different numbers of pages. Perhaps that's not the same thing?
Sub summary is appear with sorting on a field, so you need one field per one optional page. It sounds not the way to go.