Pdfpages is a LaTeX package that lets you drop individual pages of other pdfs into your LaTeX documents. Put it together with the \foreach command provided by pgf/TikZ, and you can get quite a bit done very simply.

For instance, you can scan in somebody’s photocopy of a paper from 1978 using the office printer, which emails you a pdf of the scan, and run it through this file to get a single page of the original on each page of the pdf:

\documentclass{article}
\usepackage{pgffor}
\usepackage{pdfpages}
 
\begin{document}
 
% Paper starts on a right-hand page of the original book,
% we don't need the final page of the paper before it.
\includepdf[pages=1,
            angle=90,
            trim={0 0 0 135mm}
            ]{Kamp78SemanticsVersusPragmatics.pdf}
 
% For each double-page spread, rip out the left hand then
% the right hand side. The trim was set by eye.
\foreach \page in {2,...,17} {
  \includepdf[pages=\page,
              angle=90,
              trim={0 135mm 0 0}
              ]{Kamp78SemanticsVersusPragmatics.pdf}
  \includepdf[pages=\page,
              angle=90,
              trim={0 0 0 135mm}
              ]{Kamp78SemanticsVersusPragmatics.pdf}
}
 
\end{document}

(This also gives me a chance to show off try out my new code-formatting plugin. Pretty!)