Sign a Document Here are the steps to add a Digital Signature to a spreadsheet. We'll go to the Backstage.   3. Try it: Add a Digital Signature Go to File ->Info->Permissions. Go to Protect Workbook. Click on Add a Digital Signature.   What Do You See? You will be prompted to enter the Purpose for signing this document. The notice also indicates that this signature will not be visible within the data.   Try This, Too: Type the Purpose Purpose: To encrypt confidential sales data Click on Sign.   You should see a Signature Confirmation. Click OK and keep going... File ->Info->Permissions->Protect Workbook->Add a Digital Signature Exam 77-888: Microsoft Excel Expert 2010 1. Sharing and Maintaining Workbooks 1.1. Apply workbook settings, properties, and data options: Add a Digital Signature