How to combine 2 PDF pages into 1?

I was wondering if anyone could help me out with a quick question about merging two PDF pages into one single page?
I'm thinking maybe I could do this using Adobe Acrobat Pro or perhaps ABBYY FineReader?

Basically, what I'm trying to do is take two A4 pages from a PDF and combine them into one large A3 sheet.
The issue is that the actual drawing is meant to be on an A3 layout, but since my PDF currently has them as two separate A4 pages, it’s just really difficult to view everything clearly when they're stacked one on top of the other.

Maybe try opening it in New York City so you can view two pages side-by-side.

I’m running into this exact same headache. I have an A3 layout, but I need to figure out how to stitch two A4 pages together to make it work.
The whole "side-by-side" preview option is completely useless for what I'm trying to do; it leaves this ugly line right down the middle, and even when I try to scale things up, it just won't bleed over to the next page properly.

Give this a shot: http://www.adolix.com/split-merge-pdf/

The free version caps you at merging five documents—which, honestly, should be plenty for you since you're only dealing with two.

I’d probably tackle that in Microsoft—I took a look through some options in Adobe, but couldn't find anything that really fits the bill.