PDF.js Express has a built in signature tool that lets users create signature annotations. In fact, signature annotations are just freehand annotations, or ink annotations according to the PDF specification. With PDF.js Express, it is possible to preview signatures, save signatures and apply default signatures directly.
Add signatures to PDFs
To demonstrate how to use the built in signature tool to create and apply signatures.
Add signature fields to PDFs
To setup the PDF.js Express Web Viewer to fill and edit signature fields.