If you have recently changed your password, you may be unable to print from your Mac until you have updated the saved password. Here is a quick and easy way change your saved password.
Open the Printer queue that you're unable to print to. If you just printed you can find it in your Dock. Otherwise you'll need to look for it in System Preferences.
In the printer queue hit the reload button (the curved arrow) that's to the right of the X button.
You'll be prompted for your username and password.
Be certain to check the box below the password field to add the password to your keychain.
Only follow these steps if you know what you're doing. Deleting the wrong entry out of keychain can prevent certain parts of your operating system from functioning properly.
Search for Keychain Access in Spotlight search by pressing command-space or click the magnifying glass in the upper right corner of the screen.
Under the login keychain, search for the name of the printer you are trying to print to (i.e. PublicToshibas or PRINTERS-South304).
Right or control click on the entry and choose Delete from the list of options. Click Yes if prompted.
Print your document again. You should be prompted to put in your username and password again. Check the box to save your credentials to the keychain again.