Add or remove a digital signature in Office documents

This topic explains what a digital signature (also called digital ID) is, what it can be used for, and how you can use digital signatures in Microsoft Office Word 2007, Microsoft Office Excel 2007, and Microsoft Office PowerPoint 2007. For more information, see the white paper Digital Signing of Microsoft 2007 Office System Documents.

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What is a digital signature?

Digital signatures is used to authenticate (authenticate: The process of verifying that people and products are who and what they claim to be. For example, confirming the source and integrity of a software publisher's code by verifying the digital signature used to sign the code.) digital information — such as documents, e-mail messages, and macros — by using computer cryptography. Digital signatures help to establish the following assurances:

  • Authenticity     The digital signature helps to assure that the signer is who he or she claims to be.
  • Integrity     The digital signature helps to assure that the content has not been changed or tampered with since it was digitally signed.
  • Non-repudiation     The digital signature helps to prove to all parties the origin of the signed content. "Repudiation" refers to the act of a signer's denying any association with the signed content.

To make these assurances, the content creator must digitally sign the content by using a signature that satisfies the following criteria:

The 2007 Microsoft Office system programs detect these criteria for you and alert you if there is a problem with the digital signature. For more information, see the article How to tell if a digital signature is trustworthy. You can also get or create your own digital signature, or learn more about digital signatures in macro projects.

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How can digital signatures be used in Office documents?

There are two different ways you can use digital signatures to sign Office documents. You can either:

  • Add visible signature lines to a document to capture one or more digital signatures.
  • Add an invisible digital signature to a document.

The differences between these two methods and details about how to digitally sign a document in either of these two ways are described in the following sections.

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Add one or more signature lines to a document

The 2007 Microsoft Office system introduces the ability to insert a signature line into a document. You can insert signatures lines only into Word documents and Excel workbooks.

A signature line looks like a typical signature placeholder that might appear in a print document, but it works differently. When a signature line is inserted into an Office document, the document author can specify information about the intended signer, as well as instructions for the signer. When an electronic copy of the document is sent to the intended signer, this person sees the signature line and a notification that his or her signature is requested. The signer can click the signature line to digitally sign the document. The signer can then either type a signature, select a digital image of his or her signature, or write a signature by using the inking feature of the Tablet PC. When the signer adds a visible representation of his or her signature to the document, a digital signature is added simultaneously to authenticate the identity of the signer. After a document is digitally signed, it will become read-only to prevent modifications to its content.

Document with signed signatures lines

The ability to capture digital signatures by using signature lines in Office documents makes it possible for organizations to use paperless signing processes for documents like contracts or other agreements. Unlike signatures on paper, digital signatures can provide a record of exactly what was signed and they allow the signature to be verified in the future.

To add a signature line to a document

  1. Place your pointer in the location in your document where you want to add a signature line.
  2. On the Insert tab, in the Text group, point to the arrow next to Signature Line, and then click Microsoft Office Signature Line.
  3. In the Signature Setup dialog box, type information about the person who will be signing on this signature line. This information is displayed directly beneath the signature line in the document. Do any of the following:
    • Type the signer's name in the Suggested signer box.
    • Type the signer's organizational title (if any) in the Suggested signer's title box.
    • Type the signer's e-mail address (if any) in the Suggested signer's e-mail address box.
  4. If you want to provider the signer with any instructions, type these instructions in the Instructions to signer box. These instructions are displayed in the Signature dialog box that the signer uses to sign the document.
  5. If you want the signer to be able to add comments along with the signature, select the Allow the signer to add comments in the Sign dialog check box.
  6. If you want to show the date when the signature is added in the signature line, select the Show sign date in signature line check box.
  7. Click OK.
  8. To add additional signature lines, repeat steps 1 through 7.

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Sign the signature line in a document

When you sign the signature line in an Office document, you add both a visible representation of your signature and a digital signature.

  1. In the document, double-click the signature line where your signature is requested.
  2. In the Sign dialog box, do one of the following:
    • 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.

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Add an invisible digital signature to a document

If you do not need to insert visible signature lines into a document, but you still want to provide assurance as to the authenticity, integrity, and origin of a document, you can add an invisible digital signature to the document. You can add invisible digital signatures to Word documents, Excel workbooks, and PowerPoint presentations.

Unlike an Office signature line, an invisible digital signature is not visible within the contents of the document itself, but recipients of the document can determine that the document has been digitally signed by viewing the document's digital signature or by looking for the Signatures button on the status bar at the bottom of the screen.

Signatures button on the status bar

After a document has been digitally signed, it becomes read-only to prevent modifications.

  1. Click the Microsoft Office ButtonButton image, point to Prepare, and then click Add a Digital Signature.
  2. If you want to state your purpose for signing the document, type this information in the box under Purpose for signing this document in the Sign dialog box.
  3. Click Sign.

Digitally sign with a stamp

This topic explains how you can digitally sign a Microsoft Office document with a stamp in Word documents and Excel workbooks. If a document is changed after it is signed, the signature is invalidated.

Sign an Office document with an image

When you sign the stamp signature line in an Office document, you add both a visible stamp and a digital signature.

  1. In the document, double-click the stamp signature line where your signature is requested, and then click OK.
  2. In the Sign dialog box, click Select Image.
  3. 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.
  4. Click Sign.

Insert a stamp signature line into an Office document

The feature is only available if you:

  • Are using the Chinese (Simplified), Chinese (Traditional), Japanese, or Korean language version of Microsoft Office, or
  • Installed the 2007 Microsoft Office system Multi-Language Pack for one of these languages, or
  • Enabled support for one of these languages through the Microsoft Office Language Settings.

 Note   Stamp signature lines are only available for Word documents and Excel workbooks.

  1. Place your pointer in the location in your document where you want to add a signature line.
  2. On the Insert tab, in the Text group, point to the arrow next to Signature Line, click Stamp Signature Line, and then click OK.
  3. In the Signature Setup dialog box, type the information about the person who is signing this document. This information is displayed in the stamp signature line. Do any of the following:
    • Type the signer's name in the Suggested signer box.
    • Type the signer's organizational title (if any) in the Suggested signer's title box.
    • Type the signer's e-mail address (if any) in the Suggested signer's e-mail address box.
  4. If you want to provide the signer with any instructions, type these instructions in the Instructions to signer box. These instructions are displayed in the Signature dialog box that the signer uses to sign the document.
  5. If you want the signer to be able to add comments along with the signature, select the Allow the signer to add comments in the Sign dialog check box.
  6. If you want to show the date when the signature is added in the signature line, select the Show sign date in signature line check box.
  7. Click OK.
  8. To add additional stamp signature lines, repeat steps 1 through 7.

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Remove a digital signature from an Office document

You can remove a digital signature from a Microsoft Office document that has been digitally signed.

  1. Open the document that contains the signature you want to remove.
  2. Click the Microsoft Office ButtonButton image, point to Prepare, and then click View Signatures.
  3. In the Signatures task pane, point to the signature that you want to remove, click the arrow that appears on the right, and then click Remove Signature.
  4. When you are asked if you want to permanently remove the signature, click Yes.

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Applies to:
Excel 2007, PowerPoint 2007, Word 2007