Reporting Services - Page Breaks and PDF Files
In Reporting Services reports, page breaks occur when the size of the body exceeds the page size. The crux of the lesson I learned is that the size of a sub-report cannot exceed the size of the parent containing it. Funny page breaks occur in the PDF output if this is the case.
Brian Welcker posted some terrific details on how page breaks work in Reporting Services, this post is essential if you are creating reports.