35. A system comprising: an output device; and a computer programmed to perform operations comprising: receiving a digital document that defines a presentation structure and includes a digital signature, the digital document specifying a representation of the digital signature and a location in the presentation structure for the representation of the digital signature; determining a status for the digital signature; associating a status representation with the digital signature, the status representation identifying the status determined for the digital signature; without altering the representation of the digital signature, presenting at least a portion of the digital document and the status representation of the digital signature in a user interface, the status representation being presented in the presentation structure at a location that depends upon the location in the presentation structure for the representation of the digital signature; and presenting information in the user interface about the status determined for the digital signature in response to a user input, wherein the user input comprises an indication of a selection of the digital signature in the user interface.
35. A system comprising: an output device; and a computer programmed to perform operations comprising: receiving a digital document that defines a presentation structure and includes a digital signature, the digital document specifying a representation of the digital signature and a location in the presentation structure for the representation of the digital signature; determining a status for the digital signature; associating a status representation with the digital signature, the status representation identifying the status determined for the digital signature; without altering the representation of the digital signature, presenting at least a portion of the digital document and the status representation of the digital signature in a user interface, the status representation being presented in the presentation structure at a location that depends upon the location in the presentation structure for the representation of the digital signature; and presenting information in the user interface about the status determined for the digital signature in response to a user input, wherein the user input comprises an indication of a selection of the digital signature in the user interface. 43. The system of claim 35 , wherein presenting the status representation of the digital signature includes presenting the status representation in response to user input.