Cups "add printer" page returns forbidden on web interface

Update: On Fedora 25 this is now default... So if you're having this problem on Fedora 25+, you likely messed up your config or you have a different problem. But this might still be useful users of old installs of CentOS/RHEL... you should not be using Fedora 24 at this point.

Find /etc/cups/cups-files.conf as root. Look for the line with SystemGroup sys root add wheel to it.

The following two liner should do it for you on Fedora 24

 sudo sed -i '/SystemGroup sys root$/ s/$/ wheel/' /etc/cups/cups-files.conf
 sudo systemctl restart cups

I had to combine two other answers for Ubuntu, and the solution is to add myself to the lpadmin group:

sudo usermod -a -G lpadmin your-username

For every system, the solution should be:

• Open the file /etc/cups/cups-files.conf.
• Find the group name at the line containing SystemGroup.
• Add yourself to that group (command above) and apply it (reboot for example).

The solution is

sudo usermod -a -G sys YourUser

I wrote a more detailed article on how to debug such issues.