A document authenticating method is disclosed by which a plurality of two-dimensional barcode stamps are generated and printed on a back side of the document forming a pre-defined special pattern. The barcode stamps collectively encode the content of the document to be used for document authentication. Each barcode stamp encodes linking information indicating the position of the next barcode stamp. An index barcode may be printed on the front side of the document which encodes the position information for all of the barcode stamps on the back side.