All of the Pharos printers, except for the color laserjets, print double-sided from Windows by default; Mac systems usually default to the previous print job's settings.
NOTE: Please see this FAQ for double-sided printing using the Pharos Print Center website.

If you are using a computer that is already connected to the Pharos print system, bring up the full Print options window (select File - Print from the upper left menu of the program you're using) and adjust the settings as desired. When printing double-sided you should select long edge for portrait oriented pages and short edge for landscape oriented.

Windows

Look for a Print on both sides of paper option in the main Print window.
If you don't see it, select Properties (or Preferences) and look for 2 sided: or a Print on both sides option, which may be under a Layout heading.

Macintosh

Select the Layout option in the middle of the Print window (you may need to click a Show Details button in the lower left first), then your desired option from the Two-Sided drop down menu in the lower right.
NOTE: If you don't see a Layout option, look for and select More Settings and/or Print using the system dialog… links.