Only non-null GoLayer.Identifiers of the layers of the other document are checked for presence in this document. No GoObjects are inserted or removed from any layer. No pre-existing layers are removed or reordered. The DefaultLayer property is changed to match that of the other document too, if its DefaultLayer has an identifier. The LinksLayer is also updated to match that of the other document, if that layer has an identifier. The principal use of this method is to initialize a clipboard document-- CopyToClipboard.