Sometimes, you get a new printer with a duplex feature, and your Mac, for whatever reason, decides that it should print on both sides of the page by default. (I think this is a problem with the HP printer driver installer, actually.)
Fixing this is doable, but…not obvious. At all. Here’s what you do:
- In the Finder, click the “Go” menu (four over from the Apple menu)
- Choose Utilities
- In there, open Terminal
- At the prompt, type “sudo cupsctl WebInterface=yes” and press return (without the quotes)
- Type your computer password (you won’t see it as you type) and press return
- Terminal should simply respond with a prompt like the first prompt, and nothing else. Quit Terminal.
- In Safari or another browser, go to http://localhost:631
- You should see a screen titled “CUPS”. Click the “Printers” tab. (If you get asked for a password, use your computer user’s short user name, and your usual computer password. If you don’t have the short user name, see this Apple Support article.)
- Click your printer in the “Queue Name” column
- In the rightmost of the two dropdowns, choose “Set Default Options”
- I don’t know exactly what options you’ll see next, but one of them should pertain to 2-sided printing. Set it to “Off”.
- Click the “Set Default Options” button.
- You’re done; you can close the browser window.
H/T to the helpful people in this Apple Support thread.
Photo by tom_bullock, courtesy Flickr Creative Commons.