You may deactivate your print(s) by first going to the Submit menu at the top of each deviantART page and choosing Manage Prints from the drop down menu. You will then select the Your Products link.
To deactivate one or more items, check the checkbox(es) beside the desired print(s) and click 'Deactivate Selected Prints'. To re-activate inactive prints, check the checkbox(es) beside the desired print(s) under 'Inactive Prints' and click 'Reactivate Selected Prints'.