using bookmarks as a table of contents

Help, I'm a fairly new user! I've compiled a very large PDF document from multiple files and and created the table of contents (TOC) as bookmarks. I've shared the file on dropbox for edit and review with the active bookmark TOC. It works very well for me, but when I upload it to dropbox for review - the bookmarks do not display - only thumbnails. And if its downloaded and saved or printed to PDF from dropbox the bookmarks are not included when opened in Reader?  Am I missing something?  Help...