Open and edit PDF document simultaneously in two windows

I am currently studying on a very long PDF, about 1600 pages. I have two copies of the same PDF open in full screen, and I use the first (A) to read and highlight, and the second (B) to search for images and references. So if I am on page 200 of A, and it refers to an image on page 270, instead of scrolling 70 pages and losing track of where I was I scroll on B.

That being said, I tend to highlight on both copies, and I would like to have unified highlights and comments. Is there a way to:

a) merge the comments and highlights after I close both files

or

b) instead of having two copies of the same file A and B, open two windows of the same file A and merge modifications