Google Docs' drawing tool can be used to add a signature to your document, but it's more secure to use an add-on, like DocuSign or HelloSign.

You can add a signature in Yahoo Mail to the bottom of every email you send and customize it using fonts, images, and more.

Firstly, you need your signature in digital form, preferably using a tablet PC with pen input. If you don’t have such a device to hand, sign on a white sheet of paper and take a photo of your ...