By default when an article is created it will be set to version 1. Every time a change is successfully published, the version number will increase. You can view the version number in the Stats page of any article.

However, when you are copying in existing policies, you may already have a version number for that document. You can force a specific version number for an article by overriding it. You must be an administrator to do this. Simply go to the article, then go to Explore mode, then click the "Article Info" tab along the bottom. Then, on the left side click the action menu and select Override Version:

In that form you can specify the new version. The version number must be a single integer value, it cannot contain a period. 

Tags: #NewInV4