Idea in short: pin the page you are interested in to the left side of your screen while continuing to work with the rest of your document.

As a finance professional, while working with pdf documents, I have to print them out in order to be able to compare some numbers on two different pages or from two different documents. While it is possible to open two documents and compare the pages you are interested in (although the process of arranging two documents on one screen is not as smooth as I wish it be), comparing numbers in one document on pages for example 1 and 5 is hard without printing. I believe that an option to pin the page you are interested in (with it’s automatic placement to the left side of the screen at half-screen size) with the possibility of working through the other parts of the documents, will significantly decrease the need of printing out and will reduce the use of paper.
2 versions:

1) Working with two documents: open two documents in this “pinned way” and both documents will be automatically sized to the ½ of the screen. Pin the page on one of the documents while continuing to work with the second.

2) Working with one document: Open the document. Pin the page and it will be automatically sized to the ½ of the screen (left of right side) while you can continue to work with the rest of the document.