When a document is updated/edited it will change the version number in the upper right hand corner of the original post, If you look at this link below you will see it is currently on Version 37
I wasn't clear enough. There is a feature on this site of content changes triggering stream updates, so you can be notified when content is edited. For editing documents, there is a check box for minor vs. major updates, so that notifications aren't triggered for minor document updates. But that check box is only available for Documents, not Discussions, Blogs, or comments/replies to Documents, Discussions, and Blogs. Similar capability is needed for triggering stream updates for major changes to any of these different content types.
When a document is edited, the author gets to control whether a stream update is triggered, using the "minor update" check box. But there is no similar check box when editing blog posts, or discussion posts, or comments/replies to documents, blog posts, or discussions, even though it is just as common to make major vs minor edits to those types of content as to documents.