The Adobe site at Migrating an existing site to another site has a link to " Dreamweaver extension" and another of the same at Editing a site using the extension for Dreamweaver with a link "Download the extension for Dreamweaver CS5 and CS4" that both end up in frustrating dead-ends.
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It may be worth them sorting those if you come across those pages, but as a note - they are old guide docs.