The present invention provides a printer responsive to commands from printer driver software. The printer driver software is characterized by being responsive to two types of input data. One of the types includes text data, and the other of the types includes watermark data. The two types of data are separately applied to printer driver software, rather than integrated together prior to application to the printer driver software.

An information embedding device, comprising: a memory; and a processor configured to execute a procedure, the procedure including: from an image, detecting, as an embedding target pixel block, a pixel block having a pixel value that, after being changed by a specific value corresponding to information to be embedded into the image, will be within a first specific range of an average value of pixel values of a surrounding pixel block; and changing the pixel value of the detected embedding target pixel block by the specific value.

Some implementations may provide a computer-implemented method for validating a digital document, the method including: receiving, at a computing device, the digital document comprising at least two digital watermarks, the digital document issued by a central entity; retrieving a first digital watermark from the digital document, the first digital watermark visually presented at a first time point; retrieving a second digital watermark from the digital document, the second digital watermark visually presented at a second time point, the second digital watermark being different from the first digital watermark and the second time point being different from the first time point; and reading the digital document based on the retrieved first and second digital watermarks.

Examples disclosed herein relate to providing access to digital content using a machine-readable link. As an example, an annotation comprising digital content, for a portion of a digital content, is identified in response to a print request. Based on the annotations, a machine-readable link associated with the digital content is generated. Subsequently, a printable format version of the digital document comprising the machine-readable link, and excluding the annotation is obtained wherein the machine-readable link is readable by a computing device to obtain access to the digital content over a communication network.