Add a data signature to my email button that is using a MailTo

I have the an email button on a form with the following code. 

var subject = "text";

var body = "text";

var myDoc = event.target;

try {

     myDoc.mailDoc ({

     bUI: false,

     cTo: 'email address',

     cSubject: subject,

     cMsg: body,

     cSubmitAs: "PDF"

     });

} cach (e) {

}

I would like to add data signature to this button.  Therefore, I am just wondering is there a way to do?

Any help would greatly be appreciated!

BT