How do I extract page destinations from bookmarks?
This article explains how one can determine which page a particular bookmark refers to.
This means that one will need to inspect the actions in order to determine whether a Bookmark actually jumps to a page, and if so, which one.
Please also note that an internal destination may have undefined values (NaN) for its destination rectangle. Some destinations will have no valid rectangle at all, and will just refer to some page index.