That is, how individuals add their own handwritten signatures to electronic documents. 1) Only for users of Apple computers, Mac computers have their own "preview" default application. 2) Open a pdf document (picture files are also supported), which will be opened directly through the "Preview" application by default. 3) Click the "Mark" button in the small toolbox on the toolbar. 4) Click the "Signature" icon again, and a prompt will pop up to generate a signature using the "touchpad" or "camera". In the actual test, it is best to use the "camera" to scan the handwritten signature picture. You can also search a website online to draw.