If a signature is not validated in a PDF, we see Validity unknown with a question mark. You need to validate the signature to make it valid.

Or, you can use the Save as button to create a new PDF document with a handwritten signature. So, this is how you can easily sign a PDF document in Microsoft Edge using its native draw feature.

Signing documents the old fashioned way? Ditch that pen for good! Here’s how to easily create a digital signature using your phone.

You can edit a PDF on your Mac with Preview, an app that's built-in to your computer from the start. You can use this program to edit photos, too.