The GeoServer print extension is a community module that gives GeoServer the ability to generate output in a number of formats using a template system. The primary output for the extension is PDF; this can then be sent to a printer or other users.
Note
There are two types of extensions available for GeoServer: official extensions and community extensions. Official extensions form a part of the official release, are maintained, and should be considered stable. Community extensions are not part of the official release and should be considered experimental or pending. Some community extensions, such as the print extension, have been available for a long time and are reasonably stable.
The print extension itself is a container for the MapFish printing service, which provides an HTTP API interface for printing. The interface can be called from any mapping application that can make web calls, for example, JavaScript mapping applications. More details on MapFish printing...