Help:Extension:Duplicator

As taken directly from the extension page on MediaWiki:

Usage
To duplicate an article, go to the Special:Duplicator page. On article pages, a convenient link is provided in the toolbox which will pre-populate the source page title when used.

Enter the title of the article to be copied and the destination title in the appropriate fields, and select whether or not to duplicate the associated discussion page. The latter option will not be presented if the discussion page does not exist.

Click the Duplicate button to perform the operation. You will be advised when this is complete, or in the case of errors. The copy will be logged in the destination page history, and an entry will be created in the recent changes list.

Note that it is not possible to duplicate a page which has more revisions than the configured limit (see below), and it is not possible to overwrite an existing page.