In Preview, Command-D will allow you to bookmark the current page of the PDF for later reference. However, when viewing the PDF in two-up mode (Command-3), it will always bookmark the right-hand page. How can I bookmark the left-hand page for those times when it's that page precisely that I want to bookmark?
I do not know how to do that with Bookmarks, but I use a work around till Apple does something.
Instead of bookmarks I use Highlights and Notes (alt+cmd+4)
Then I place a Note on appropriate page (left or right) or anywhere.
The advantage is I can make comments in the note.