As a simple workaround for the "flip between two pages" feature that is so easy in dead tree but harder on computers, I usually just open the pdf twice, if the

As a simple workaround for the "flip between two pages" feature that is so easy in dead tree but harder on computers, I usually just open the pdf twice, if the software allows two running copies, or if the software is too clever, I just copy the pdf into a second copy and open that. I can then alt-tab between them and scroll to different parts. On the phone, I can use Acrobat Reader and Koreader at the same time.