The documentation link for admin/settings.php?section=authsettingldap (i.e. the auth_ldap config page, Site administration -> Plugins -> Authentication -> LDAP server) is wrong. It points to:

http://docs.moodle.org/33/en/admin/setting/authsettingldap

The documentation is at:

https://docs.moodle.org/33/en/LDAP_authentication