A signature line resembles a typical signature placeholder that might appear in a printed document. However, it works differently. When a signature line is inserted into an Office file, the author can specify information about the intended signer, and instructions for the signer. When an electronic copy of the file is sent to the intended signer, this person sees the signature line and a notification that their signature is requested. The signer can:

Type a signature, or

Select a picture of an inked signature, or

Write a signature by using the inking feature of a touch-screen PC

When the signer adds a visible representation of a signature to the document, a digital signature is added at the same time to authenticate the signer's identity.

Create a signature line in Word or Excel

  1. In the document or worksheet, place your pointer where you want to create a signature line.

  2. On the Insert tab, in the Text group, click the Signature Line list, and then click Microsoft Office Signature Line.

  3. In the Signature Setup dialog box, type information that will appear beneath the signature line:

    Suggested signer The signer's full name.
    Suggested signer's title The signer's title, if any.
    Suggested signer's e-mail address The signer's e-mail address, if needed.
    Instructions to the signer Add instructions for the signer, such as "Before signing the document, verify that the content is correct."

  4. Select one or both of the following check boxes:

    Allow the signer to add comments in the Sign dialog box: Allow the signer to type a purpose for signing.

    Show sign date in signature line: The date the document was signed will appear with the signature.

Sign the signature line in Word or Excel

When you sign a signature line, you add a visible representation of your signature and a digital signature.

  1. In the file, right-click the signature line.

  2. From the menu, select Sign.

To add a printed version of your signature, type your name in the box next to the X.

To select an image of your written signature, click Select Image. In the Select Signature Image dialog box, find the location of your signature image file, select the file that you want, and then click Select.

To add a handwritten signature (Tablet PC users only), sign your name in the box next to the X by using the inking feature.

Click Sign.

The Signatures button appears at the bottom of the document or worksheet.

The following image shows the Signatures button.

Source: Microsoft - https://support.microsoft.com/en-us/office/add-or-remove-a-digital-signature-in-office-files-70d26dc9-be10-46f1-8efa-719c8b3f1a2d#__toc311526850