Beginning with V-Ray 5 for 3ds Max, we’ll support only the current V-Ray version in the online documentation. For V-Ray for 3ds Max, that is V-Ray for 3ds Max.
Older versions are available for offline use as simple html files packed in an archive, along with all the assets (screenshots, renders, files). For Max, here is the page where you can download them: [Chaos Docs
The same will follow for all Chaos documentation upon a release of a major version for each product.
It would be nice to also get an archive of the VrayforC4D 3.7 documentation
there is nothing online anymore neither on chaosgroup.com nor on vrayforc4d.net/docs/
The old 3.7 documentation that was hosted on docs.chaosgorup.com wasn’t full and only contained a few pages with the release notes for V-Ray 3.7 and how to setup Distributed Rendering and render in Chaos Cloud nothing more.
As for the documentation on Vrayforc4d it was never maintained or owned by us because it was related to V-Ray 3.6, so about this you need to ask @Stefan_Laub for more information.