This example shows how to use the
GeoExt.data.MapfishPrintProvider class to talk to a
Mapfish Print Server (v3.x).
Afterwards we have all information to create a valid POST to the servlet. The printed extent is highlighte as vector layer. If you move around or change the zoom, the extent will adjust accordingly.
Click the button labelled 'Print' to actually create a PDF for the displayed extent.
Have a look at basic-mapfish.js to see how this is done.