Don’t want to scan your signature on paper or use your MacBook’s trackpad to sign digital documents or PDFs? No problem. macOS Catalina users can just open the Preview App and sign it using their iPad or iPhone.
Within the Preview app, head to Tools, then Annotate, then Manage Signature and Create Signatures. Under the same section, there will be an option to choose an iPad or iPhone.

Devices that are on iOS 12 will show up, but only those that have iOS 13 will be able to create signatures. On compatible devices, a new signature interface comes up and you’ll be able to create your very own using a Pencil or your finger. Tap done and the signature will come up the next time when you get to the Preview app.
The iPad and iPhone already have Markup features for digitally signing PDFs, but the Preview option is great if you’re working on a Mac.