How to open 2 Adobe Reader instances?
Solution 1:
Just go to the upper menu and click "Window">"New Window".
Then you'll have two instances of one document opened in separate windows.
Solution 2:
You could make a (temporary) copy of the PDF in question, with a different name, and then open them both in Adobe Reader.
Solution 3:
In Reader 20145.010.20060 you can simple drag and drop from the tab in the Reader window and another window will appear
Solution 4:
Yeah, you can do this with Adobe Acrobat, but sadly, not Reader. I'd go ahead and download Foxit anyways. Or CutePDF.