Bookmarks
Document bookmarks
A PDF file can contain bookmarks that are created during the authoring process of the document. Therefore they can not be changed or removed from the document. These bookmarks are often like an index for the document. They are displayed in the bookmark-sidebar on the right side of the viewer.
User-specific bookmarks
It is also possible to create bookmarks for specific pages of the document.
caution
At this point, user specific bookmarks are only present while the document is open. If you need to persist them, consider using the jadice web toolkit instead.