Many Linux applications will generate a new configuration file if there is not an existing one when the application starts and so I suggest you rename the existing configuration file to see if this happens:
Then reboot the PC and if you take a look at /etc/cups/ you will hopefully see that a new cupsd.conf file has been generated. Configure this file as required, either through the various GUIs or directly with a text editor.
sudo mv /etc/cups/cupsd.conf /etc/cups/cupsd.conf_old
If a new file has not been automatically generated then take a look in the /etc/cups/ directory again and you may find a file called "cupsd.conf.default" which could be copied manually and then renamed as "cupsd.conf":
Reboot and configure as before.
sudo cp /etc/cups/cupsd.conf.default /etc/cups/cupsd.conf