Thanks for raising this question for how to share content between your Jive Cloud environment in different places. I don't believe this is currently possible, although there are some ways to share content without having to maintain separate copies of the same document.
In Jive Cloud, you may share content with other places. To do this, click on "Share" while viewing the document and enter the name of the place you'd like to share it with. Unfortunately, visibility will be limited to users who have access to the existing place where the content was posted, otherwise, they will simply see a link to it. The catch is that external contributors will only have access to their immediate externally accessible groups, so this limits the usefulness of the sharing functionality when sharing site wide.
If this is an important feature you'd like to see in the future, I would encourage submitting a feature request idea in the Ideas for Jive space to capture this requirement and use case. Let me know if you have any other questions in the meantime.