1. A method for digitally signing an electronic document with a user-entered image of a signature, the method comprising: rendering the document; examining properties of each of a plurality of signing certificates available to the user; in response to examining the properties, filtering out signing certificates that are used for network authentication and for code signing from among the plurality of signing certificates to determine signing certificates that match a selection criterion; selecting a signing certificate from among the signing certificates that match the selection criterion; rendering a sign dialog associated with the document; receiving a signature from a user, wherein receiving the signature from the user comprises receiving a written signature from the user; creating a digital representation that includes an image of the written signature of the user; creating a single unique value, the single unique value representative of both the image of the written signature of the user and of the document; and saving the unique value in association with the document thereby digitally signing the document, wherein saving the unique value in association with the document includes associating the unique value with the signing certificate selected.
3. The method of claim 1 , further comprising: locking the document from edits to secure the authenticity of the document; and forwarding the document to another user for a second signature.