Certain routers like the Asus RT-N66U have built-in network print server capability, which is an under-appreciated feature IMHO. But the settings > add printer dialog in Ubuntu 14.04 left much to be desired when it could not add the printer running behind the Asus router.
As a workaround, run the following command to get a better add-printer facility:
LPD/LPR Host or Printer.
Enter router IP (commonly
192.168.1.1) in “Host”, and
LPRServer in “Queue”, and select
Choose the driver that matches the printer to add it to the system. You can now print from other applications.