The present invention relates to various digital watermarking methods and systems. In one embodiment, a plurality of microlenses can provide a steganographic signal for a handheld device. The pattern corresponds to (or conveys) an identifier. In yet another embodiment, monetary objects are watermarked to signify currency denomination information. The information, once extracted, is used to provide feedback regarding the currency denomination. An audio signal or Braille output can be provided as feedback. In still another embodiment, a document management system is based on watermarks. Embedded watermarks are used to track document history, determine document version information, and enhance overall security. Handheld computing devices are advantageously employed with these embodiments.