Duplexing on Windows

Click on File then print, or use ctrl+p.

Then click on Properties in the top right of the Print window.

Now click on the drop down menu reading Print on both sides: and choose which option is the correct one for you, click OK then proceed to print.

Duplexing on Mac's

Click on File then print, or use command+p

Click on the Copies & Pages drop down menu and click on layout.

Find the Two-Sided drop down menu then select the option that fits your needs. Following the selection click Print and you are all set with duplexing.