PDFjam, by David Firth, is a small collection of shell scripts which provide a
simple interface to some of the functionality of the excellent pdfpages package
(by Andreas Matthias) for pdfLaTeX. At present the utilities available are:

 * pdfnup, which allows PDF files to be "n-upped" in roughly the way that psnup
   does for PostScript files.
 * pdfjoin, which concatenates the pages of multiple PDF files together into a
   single file
 * pdf90, which rotates the pages of one or more PDF files through 90 degrees
   (anti-clockwise).

WWW: http://www.warwick.ac.uk/go/pdfjam