This is functionality that currently doesn't exist in GNOME; forwarding upstream to the GNOME bug developers who have a feature idea open:
http://bugzilla.gnome.org/show_bug.cgi?id=355691 -- Gnome offers no GUI way to manage fonts https://launchpad.net/bugs/66833 -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs
