Editing PDF

Hey, I was wondering if anyone here was skilled in editing PDF's and could help me out. Basically I have a PDF file that is a bunch of photocopies and there is a ton of blank space on each page, enough that I can combine every two pages. I am wondering how I would go about doing that(trying to save paper/money in printing). I have unlocked versions of Acrobat and Photoshop, they aren't the newest versions but I am guessing that is all I need. I tried opening the PDF in Photoshop but I don't know how to switch between pages to edit them. Then I also don't know how to save it as the combined PDF. Uh...if anyone understands what I am trying to do and can help I'd greatly appreciate it.