1. A method of recovering content information from a watermark in a target digital document to be carried out by a computer adapted to perform the steps of: locating the watermark in the target document based on a pre-determined template specification that describes a manner in which the watermark was merged into the target document, the template specification identifying at least one watermark specification and providing a mapping list indicating a manner in which at least one watermark associated with the at least one watermark specification is merged into a document; and obtaining the content information from the located watermark according to a watermark specification identified by the template specification, the watermark specification identifying a specific watermarking technology and a target object into which the watermark was placed.