On trelby site, under the downloads, you can get the Courier 10 BT
font, which is thicker than the default windows Courier, and looks
much better when printed.
On windows you can change to any other monospace font, like fixedsys,
etc. But courier is the standard for screenplays, so you should just
grab the font from the site. Just google for monospace free fonts, and
you should get a good list of options.