Is there a version of the documentation online suitable for linking?

This is not a new problem. People have solved this problem in practice.

Basic principles off the top of my head:

1. URLs for the latest version of the software should have a form without a version dependency. This is what users like me would normally use. Rough example:

   https://devontechnologies.com/devonthink/manual/en/chapterA/sectionB/subsectionC
   

2. There should also be versioned URLs. Rough example:

   https://devontechnologies.com/devonthink/3.9.4/manual/en/chapterA/sectionB/subsectionC
   

3. The server should have redirections for things that are removed, so that most links will automatically go to the revised versions, or at least don’t give a 404.

This will take care of 99% of it.

For good measure, it would be easy to send the whole documentation site to the Internet Archive, so that if something really goes awry, one can try to find it in the Wayback Machine.