OpenKM has many interesting features, but requires some configuration process to show its full potential.
Forum rules: Please, before asking something see the documentation wiki or use the search feature of the forum. And remember we don't have a crystal ball or mental readers, so if you post about an issue tell us which OpenKM are you using and also the browser and operating system version. For more info read How to Report Bugs Effectively.
To change the version of a document already in the OpenKM repository you must upload a new document -> that will change the version with an upper one. If you have uploaded several times the same document ( several versions ) you can go back to an older version. That's the way how document versioning it works in all the DMS.