I am having a similar problem as the original question. What I have done is exactly what you have suggested, to arrange the Bookmark sections in the order that I need them, however, the page numbers do not correspond. The Bookmark that I have as the first in the list is still marked as pg. 18. I have also done as @abracadabraJRB has said, right-clicking on the Bookmark to set a new destination, and it has still not changed the page number. This is in Acrobat Pro DC. It's a 400 page document, and I do not have the option to export and combine the PDFs all over again. I'd like the order that I've arranged the Bookmarks in the panel to be the page order. Any suggestions?