Booklets in memoir class

The pdfpages package provides an easy way to arrange the pages of a PDF file so that it can be printed as a booklet. For two A5 pages arranged on an A4 landscape paper, the correct choice of options is

\documentclass{scrartcl}
\usepackage{pdfpages}
\begin{document}
\includepdf[pages=-,booklet,landscape]{document.pdf}
\end{document}

More information, e.g. on splitting the booklet into several signatures, can be found in thepackage documentation.