If you’re using an iPad or a Mac to sign a legal document, you can do so in a much easier fashion than printing the document, signing, scanning to your computer, and emailing back to the original sender.
For the iPad:
Open the email with the PDF attachment and long-press on the file. Then tap Markup and Reply.
Now you can use your finger or Apple Pencil to sign the document and send it back–all within the Mail app.
For the Mac:
Open the PDF file in Preview and go to Tools > Annotate > Signature. If you’ve already done a signature using your iPad, it will show up here. Otherwise, click on Manage Signatures…, then Create Signature.
Here, you can sign with your finger using the trackpad, or you can sign on a piece of paper and hold it up to the camera to take a snapshot.
Once it captures the signature, you can drag the image anywhere in the document.
When it’s in the right position, save the PDF, drag it into the email, and send it off!