Using Apache with mod_jk
It's not possible to use only mod_jk to proxy Confluence 6.0 or later. This is because Synchrony, which is required for collaborative editing, cannot accept AJP connections. The preferred configuration is Using Apache with mod_proxy.
If you are unable to switch to mod_proxy, see How to configure Apache mod_jk to proxy Confluence 6.x or later for a workaround.