PosteRazor cuts a large image into smaller pieces which can be printed on regular size paper (A2, A3, A4, custom, etc.). The separate pieces can be assembled to a poster afterwards.
As input PosteRazor takes a raster image. The resulting poster is saved as a multipage PDF document. An easy to use user interface guides you through a number of steps. PosteRazor is available as a Windows, an OSX and a Linux version. It is an open source, GNU licensed project which is hosted on SourceForge.net.