You can create a nautilus script, i.e. an executable shell script (placed in a special scripts directory) that may be invoked by selecting a file or group of files in Nautilus, and right-clicking with the mouse, to bring up a context menu. One of the options in this menu is the 'Scripts' submenu, which allows you to select a script to invoke on the selected files.
The submenu 'Scripts' only appears once you have at least one script in the scripts directory.
Follow these steps (replace every occurrencies of <your_username>
with your real username):
#!/bin/bash
# send to default printer
lpr $*
Now, if you select one or more file, right-clicking them you should see the submenu 'Script' in your menu, and the subitem 'Print'.
If you don't see them, probably you need to logout and login, or reboot the system or restart nautilus (nautilus -q && nautilus &
).