17. An apparatus according to claim 13 comprising a comparison visualizer operative to present a view of at least one target document comprising a plurality of layer views, a layer view comprising pixels rendered from a plurality of graphic elements associated with a layer view, the visibility of a layer view being separately controllable.
13. An apparatus according to claim 12 also comprising a document merger, operative to create at least one target document based on the first and second documents, the first and second lists, and the edit data.