The package ps-print.el, which is now included with XEmacs, provides the ability to do this. It contains complete instructions on its use:
<xemacs_src_root>/lisp/packages/ps-print.el
lpr only works for Postscript files, so how do I get M-x lpr-region and M-x lpr-buffer to work?(setq lpr-command "Command to print text files")
Please don't forget to replace Command to print text files with the actual command (`enscript', `nenscript', etc.)!