WordPress plugin that adds a "Clone Page Tree" action to the page row actions. Cloning a page tree clones the page and all descendents creating a new copy of the full hierarchy. After clicking "Clone Page Tree" you will be redirected to edit the top-most page to allow you to give it a unique title. All cloned pages are left in draft mode.
There are many plugins out there which allow you to duplicate a post or page however this is the only one that allows you to duplicate a page and all its descendent pages in a single click.
This plugin used the page duplication script here as a starting point but then adds recursion over page children to clone the full tree.