Hi Stephen, I don't think it's a permission, but rather a menu setting.
If you go into the PDM Administration Tool, right click on Users, Settings, Menus:
Find the Update command from the list on the left-hand side, and add it to the Folder right-click menu.
This should then appear for users when they right click on a folder. You can do this for a group as well.
Hope this helps.
Ahh, I was looking for "Update values in files ..." and not a vague "Update". Thanks - this worked.