Provide clearer indication of "latest" information in docs

I am often using Google search to find our docs and it very often comes up with the 1.8 manual.

As a point of process, could we add a general banner to all of the previous version documentation that says "this is not the latest version, click here...". Ideally we'd provide a direct link to the relevant page, but even just telling people that there is updated material would be an improvement.