Document Signature
On macOS, the PDF viewer has a nice feature to add your hand-writter signature to a document.
You can write your signature on a white piece of paper and scan it through the laptop's webcam. The app the keeps this signature in memory (you can add several of them).
Then you can add that signature to a PDF. This is really handful when you want to keep a PDF low in size, instead of having to print it, sign it and scan it.