When an Excel document has a signature added to it, no edits are permitted to the document without invalidating that signature.

Create a Digital Signature in Excel First things first, to create a digital signature, you must have a signing certificate, which proves identity and verifies the authenticity of the document.

You can add a signature to an Excel spreadsheet using electronic signature software or using the Insert feature in Excel. Open an Excel spreadsheet and select Insert > Add a Signature Line.