The latest NU-WRF release is referred as version 11.5 (Ekman patch 5). Documentation is available online on this link.
Older guides:
NU-WRF User Guide (Ekman release patch 4)
NU-WRF User Guide (Ekman release patch 3)
NU-WRF User Guide (Ekman release patch 2)
NU-WRF User Guide (Ekman release patch 1)
NU-WRF User Guide (Dalton release, v10)
NU-WRF User Guide (Charney release patch 3)
NU-WRF User Guide (Charney release patch 2)
NU-WRF User Guide (Bjerknes release)
Other guides: