/usr/share/man/man8/lightdm-gtk-greeter-settings-pkexec.8.gz is in lightdm-gtk-greeter-settings 1.2.1-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/man/man8/lightdm-gtk-greeter-settings.8.gz