A method for creating an electronic signed document from an original electronic document includes: generating a document-related image based on content of the original electronic document; displaying the original electronic document; recording a real-time video of a user as the user inputs a set of signature strokes that constitute a signature; generating a superimposition video based on the real-time video and the document-related image, wherein in the superimposition video, the document-related image overlaps apart of the real-time video; and generating an electronic signed document by embedding the superimposition video in the original electronic document.