How do I change printer settings on MacBook Air?

If your credentials are not working, it would suggest your account is not an admin account or you are not a member of the print admins group (lpadmins). Is your account a standard account?

If you are an admin on your Mac, and you are comfortable with command line, you can use

lpoptions -l

to display all the options of your default printer. I will assume you only have one printer configured. This will display all of the options for the printer. An example output will look like this:

Collate/Collate: True *False
ColorModel/Color Mode: Gray *RGB
cupsPrintQuality/Quality: *Normal
Duplex/2-Sided Printing: None *DuplexNoTumble DuplexTumble
PageSize/Media Size: A4 A5 A6 B5 Env10 Env9 EnvC5 EnvDL EnvMonarch Executive FanFoldGermanLegal ISOB5 Legal *Letter Oficio Postcard Statement Custom.WIDTHxHEIGHT
MediaType/MediaType: envelope stationery cardstock labels stationery-letterhead stationery-preprinted stationery-lightweight stationery-heavyweight *any
InputSlot/Media Source: auto envelope manual tray-1

Note the syntax. The first value is the programmatic key (Duplex), the second is the human readable description (2-Sided Printing), and the final is the settable options with the active option marked with an * (None *DuplexNoTumble DuplexTumble). Initially, the printer has 2-sided printing enabled.

You can use lpstat to get the Cups printer name and then user lpadmin to modify the values of a configured printer. For example,

lpstat -v

returns

device for Home_Printer: ipps://ABCDEF123456.local.:443/ipp/print

"Home_Printer" is the Cups printer name I can now use in lpadmin. For the printer listed above, I can use the following to modify a settings:

lpadmin -p Home_Printer -o Duplex=None

The -o is the options and I a targeting the Duplex option and setting it to None. As an admin with rights to modify the printer, a sudo is not required. Repeating lpoptions -l now reports:

Duplex/2-Sided Printing: *None DuplexNoTumble DuplexTumble

Note the * is now next to None. This turns off two sided printing for this printer.

Again, you must be a local admin for this to work. If you are a local admin and access to the CUPS admin page is not working, you might try resetting the printing subsystem.

Let's start with a bit more information from you so we can have a better chance to assist you with a potential solution:

• Which exact model is your MacBook Air (MBA) and what version of macOS is it running?
• What is the exact make & model of the printer you are referring to in your post?
• How is this printer connected to your MBA? Directly, by USB, or via a wireless connection? If the latter, did you verify that both your MBA & this printer is on the same local wireless network?
• Has this always been an issue, or just started happening recently?
• What exactly have you tried, so far yourself, to resolve this so that we don't offer potential solutions that may not have already worked for you?

Ref: Writing an effective Apple Support Communities question