/etc/default/ufw: high level configuration, such as default policies, IPv6 support and kernel modules to use
    /etc/ufw/before[6].rules: rules in these files are evaluated before any rules added via the ufw command
    /etc/ufw/after[6].rules: rules in these files are evaluated after any rules added via the ufw command
    /etc/ufw/sysctl.conf: kernel network tunables
    /var/lib/ufw/user[6].rules or /lib/ufw/user[6].rules (0.28 and later): rules added via the ufw command (should not normally be edited by hand)
    /etc/ufw/ufw.conf: sets whether or not ufw is enabled on boot, and in 9.04 (ufw 0.27) and later, sets the LOGLEVEL
    /etc/ufw/after.init: initialization customization script run after ufw is initialized (ufw 0.34 and later)
    /etc/ufw/before.init: initialization customization script run before ufw is initialized (ufw 0.34 and later)

After modifying any of the above files, activate the new settings with:
$ sudo ufw disable
$ sudo ufw enable