With macOS Catalina, the Preview (Preview) application has been updated and you can sign documents / PDF files on your Mac via the iPhone running iOS 13 or iPad running your iPadOS. Previously, "signing" PDF files on Mac had only two ways: signing with Trackpad, mouse or using the computer's built-in camera to scan the signature on paper. And obviously, signing with a mouse is difficult / inconvenient, while signing on paper and scanning is "a little wrong" when finally through the traditional paper signing step. Meanwhile, with iPhone or iPad, you just swipe right on the touch screen is done, especially when using more Apple Pencil, everything is not different from the name on the paper. So why not combine it? Apple also thought about it and Preview on macOS Catalina will have a new option – that is iPhone or iPad.
To sign documents / PDF files, you will still open Tools -> Annotate -> Signature -> Manage Signatures -> Create Signatures. Steps as usual. But instead of selecting Trackpad / Camera, select iPhone or iPad. Next, select the device. (Note: Devices running iOS 12 will also appear in the list but the signature creation feature only works with devices running iOS 13 or iPad OS.).
When you have finished selecting your iPhone / iPad device, immediately there will be a New Signature screen on your device to sign by hand or Apple Pencil. Signed, done done, immediately the signature will appear immediately on the Preview application on the Mac for you to add to the document. (The feature only works if the device is unlocked, but it is still possible that the error will be fixed soon).
Screen signed on iPhone
After signing, the signature will appear on the Mac.