Geany has basic printing support. This means you can print a file by passing the filename of the current file to a command which actually prints the file. However, the printed document contains no syntax highlighting. You can adjust the command to which the filename is passed in the preferences dialog. The default command is:

% lpr %f

%f will be substituted by the filename of the current file. Geany will not show errors from the command itself, so you should make sure that it works before(e.g. by trying to execute it from the command line).

A nicer example, which I prefer is:

% a2ps -1 --medium=A4 -o - %f | xfprint4

But this depends on a2ps and xfprint4. As a replacement for xfprint4, gtklp or similar programs can be used.