1. A method of digital watermark processing, the method comprising: receiving a content signal; performing a watermark decoding on the content signal to obtain first information associated with a preexisting watermark in the content signal; from the watermark decoding, determining a watermark state of the content signal; evaluating a watermarking rule based on the watermark state to determine watermark encoding to apply to the content signal to comply with the watermarking rule; performing the watermark encoding on the content signal to embed a layer of digital watermark into the content signal; and storing an association between the first information and the watermark layer so that the watermark layer provides access to new information in addition to the first information.