seo and documenting multiple version of our software

How to markup the documentation of the different version of our product?

considering that

  • The content is not strictly identical across version,
  • but it is very often the same,
  • we wish newer version to be preferred by seo engines,
  • but older versions are preferred since they are older.

for a couple of year our strategy has been to follow this answer to the question

  • have all url prefixed by their version
  • create a “latest” prefix that is a symlink pointing to the most recent version
  • the most recent version have a <link rel="canonical" targeting the “latest”
  • all version (except the most recent) start with a disclaimer indicating that this version is not the latest, this disclaimer include a link pointing to the latest version

This is an example of our urls :

  • old version :
  • latest version :
  • latest version duplicate, with the <link rel="canonical" :

This is an example of the disclaimer including a link to the latest version picture of the link pointing to the latest version

This was meant to strengthen the “latest” url by having a stable url over time and by having several pages linking to it.

This does not seem to work, since google continues to prefer olds pages. What should we do? I only see the nuclear weapon here : adding on all version a <link rel="canonical" targeting the “latest”.