Embodiments of the present invention relate to attesting a document that contains encoded data, such as a barcode or DataGlyph. When a document contains encoded data that is not in human-readable form, the document is checked to determine whether content in the encoded data appears somewhere in the document in human-readable form. Based on the amount of content that appears in the document, the document may be marked with a seal that attests to the amount of content in the encoded data that appears in human-readable form. The seal may be visually distinctive to facilitate easy recognition by a user or device.