While the Command Center search does locate Docs that are specifically Archived, it appears that a non-archived doc attached to a space location is "Lost in Space" with their not showing up in the results. It would be great if these docs could be available still in the universal search for various reasons (e.g. troubleshooting bugs/tickets while not having to keep a previous client's space active). While I haven't tested, I suspect the same is true for docs located in archived tasks, folders, and lists.