The simplest way to do that is to add top level bookmarks wherever you want to start a new document. Once you have these bookmarks in place, you just select to split the document by top level bookmarks.
Your question suggests that you have some information in your document that would indicate how many pages should be in each segment. The problem with this is that it's hard to get that information out. You would need a custom solution to look in the correct spot and try to extract the number or whatever information you have in that location.
Karl Heinz Kremer
PDF Acrobatics Without a Net
PDF Software Development, Training and More...
http://www.khkonsulting.com