The revision at which the signature was signed.
Content can be added to a document after signature. Most
commonly this occurs if someone wishes to countersign an already
The original signature remains valid because it applies to the
original document but you may wish to indicate that the document
has been changed.
If the document has been modified in this way the
SigningRevision will be less than the Doc.ObjectSoup.Revisions.
To detect the actual visible differences you would need to
render the document at each revision using the
Note that you should check the IsModified property before relying on the
value of this property.