There is nothing in Acrobat that would allow you to do that. One option is to turn things around and delete the pages you don't want from your document, and then save that as your new document. This will keep the bookmarks for the now deleted pages in your document, but you will end up with the bookmark hierarchy you want.
One thing to keep in mind is that bookmarks can do a lot more than just get you to a page view. This means that some of these bookmarks may no longer work correctly when you do that.
You could use a 3rd part bookmark managing application to help you with this problem.
Karl Heinz Kremer
PDF Acrobatics Without a Net
PDF Software Development, Training and More...
http://www.khkonsulting.com