Acrobat Pro Missing +Bookmark icon

[QueSeraSara]

I'm trying to add bookmarks to commonly referenced elements in a file. I am in Adobe Acrobat, I have the Bookmarks window open, but the +Bookmark icon is missing (it's literally not there). If I click the ... icon the menu includes "New Bookmark from Structure" but the item is greyed out and not usable. I have a Pro liscense and am signed in.  Why is this feature absent?

[Bernd Alheit]

Is the document secured?

[QueSeraSara]

They are not. Others in my company are able to annotate and bookmark these same files.

[QueSeraSara · Accepted solution]

I have solved this. Upgrades to my Acrobat installation were either not completed, or did not take place. In following instructions found in other similar posts I submled upon a option to "Check for Updates" in the Help menu. Updating and restarting opened up all the Pro Tools (including bookmarks) that should have completed during installation.

@Adobe this was unnecessarily obtuse for the end user.