My girlfriend had a laboriously scanned document in two pieces that needed to be combined. I had a .NET command line utility that I wrote a couple years ago that does just that, but because one of the scanned pages was a different size, it got cut off in the resulting output file. So I could either try to dig up some docs on the library I used, play around with Intellisense in Visual Studio, or see if there was a Python library that might work.
2 minutes of Googling later I had pyPDF, and maybe 10 minutes after that, I had reset the mediaBox on the outsized page, written it to a new pdf file, and emailed it off. Q.E.D.