Create a webbrowser control and load the document into the browser. Then execute the following command:
object o = null;
webBrowser.ExecWB(SHDocVw.OLECMDID.OLECMDID_PRINT, SHDocVw.OLECMDEXECOPT.OLECMDEXECOPT_DONTPROMPTUSER,ref o, ref o);
Hope that gets you started.