Signing PDFs

You can sign a document to attest to its contents or approve the document. Based on the intent, you use different types of signatures.

Signature types

A document can contain certification signatures, approval signatures, or both. The signature type you need depends on the intent of both the author and the signer. Signature types include the following:

Certification signature
A certification signature provides a higher level of document control than an approval signature. Because it must be the first signature in a document, certification menu options are disabled if another signature is already present. In addition, you can control the types of changes other people may make.

Approval signature
An Approval signature is a digital signature applied to a document that is not a certification signature. All signatures other than certification signatures are classified as Approval signatures.

Both certification and approval signatures comply with data protection standards specified by the European Telecommunications Standards Institute (ETSI). In addition, both signature types comply with the PDF Advanced Electronic Signature (PAdES) standard. Acrobat and Reader provide an option to change the default signing format to a CAdES format. To view this option, go to Edit > Preferences > Security > Advanced Preferences > Creation, and expand Default Signature Signing Format list. This option is compliant with Part 3 of the PAdES standard. The timestamp capability and native support for long-term validation of signatures (introduced in Acrobat 9.1) is in compliance with Part 4 of the PAdES standard. The default signing format, when set up accordingly, is compliant with Part 2 of the PAdES standard.

Sign a PDF

You can sign a PDF to indicate your approval using either a digital signature or ink signature. Digital signatures can be used to sign a PDF multiple times and by different persons. When you sign a document, your digital signature appears in the signature field. The appearance of the signature depends on options you choose. The actual information for your digital signature is embedded in the PDF.

In Acrobat, the first person to sign a document can add a certifying signature to restrict changes to the document.

Note: To allow Reader users to sign documents using either type of signature, choose File > Save As > Reader Extended PDF in Acrobat. Then, choose an option from the list.

Sign a PDF—Quick steps

Signing is essentially a straightforward process. It can be complicated by special requirements, such as creating different signatures for different roles and adding timestamps. But to create an uncomplicated signature, follow these steps.

  1. Complete your edits before you sign. Changes made to the document after it is signed can invalidate the signature.

  2. Get a digital ID from your own organization, buy a digital ID (see the Adobe website for security partners), or create a self-signed one. See Create a self-signed digital ID. You can’t sign a PDF without a digital id.

  3. Drag your pointer to create a space for the signature.

  4. Follow the onscreen prompts to finish signing the PDF.

Sign with a new digital ID

  1. Open the PDF and choose Tools > Sign & Certify > Sign Document. If you don't see the Sign & Certify panel, see the instructions for adding panels at Task panes.
  2. If a dialog box appears, read the information and then click OK.
  3. Drag your pointer to create a space for the signature.
  4. Select A New Digital ID I Want To Create Now from the Add Digital ID dialog box.
  5. In the Add Digital ID dialog box, select a storage location for the digital ID.
  6. Type a name, e-mail address, and other personal information for your digital ID. When you certify or sign a document, the name appears in the Signatures panel and in the Signature field.
  7. (Optional) To use Unicode values for extended characters, select Enable Unicode Support, and then specify Unicode values in the appropriate boxes.
  8. From the Use Digital ID For menu, choose whether you want to use the digital ID for signatures, data encryption, or both.
  9. Type a password for the digital ID file. For each keystroke, the password strength meter evaluates your password and indicates the password strength using color patterns.
  10. Confirm your password, and click Finish.

Sign with an existing digital ID

  1. Open the document.
  2. Choose Tools > Sign & Certify > Sign Document. If you don't see the Sign & Certify panel, see the instructions for adding panels at Task panes.
  3. Click an existing signature field, or drag your pointer to create a space for the signature.
  4. In the Sign Document dialog box, complete the signature as follows:
    Password
    Type the password associated with the digital ID.

    Appearance
    Select to modify the information to be displayed in the signature, for example date and time.

    Lock Document After Signing
    If this option is available, select it only if you are the last recipient to sign the document. Selecting this option locks all fields, including the signature field.

Sign with an ink signature

Ink signatures use the default color of Pencil tool markups. To change the color of the signature, right-click the Pencil tool in the Drawing Markups panel that appears when you choose Comment > Drawing Markups. Then choose Tool Default Properties, and change the color in the Appearance tab.

  1. To sign a PDF with an ink signature, do one of the following:
    • In Acrobat, choose Tools > Sign & Certify > Apply Ink Signature. If you don't see the Sign & Certify panel, see the instructions for adding panels at Task panes.

    • In Reader, choose Tools > Extended Features > Apply Ink Signature. (This command is available only if the PDF creator enabled digital signature and commenting rights.)

      The cursor changes to a cross-hairs.

  2. Click where you want to sign and draw your signature.
  3. To include the signature with the document, save the PDF.
Note: You cannot add an ink signature to a PDF created in LiveCycle Designer ES or the LiveCycle Forms ES. PDFs created from those sources do not allow comments and markups.

Sign in Preview Document mode

When document integrity is critical for your signature workflow, use the Preview Document feature to sign documents. This feature analyzes the document for content that may alter the appearance of the document. It then suppresses that content, allowing you to view and sign the document in a static and secure state.

The Preview Document feature lets you find out if the document contains any dynamic content or external dependencies. It also lets you find out if the document contains any constructs such as form fields, multimedia, or JavaScript that could affect its appearance. After reviewing the report, you can contact the author of the document about the problems listed in the report.

You can also use Preview Document mode outside a signing workflow to check the integrity of a document.

  1. Select Edit > Preferences.
  2. From the Preferences dialog box, select Security on the left.
  3. Select View Documents In Preview Document Mode When Signing, and click OK.
  4. In the PDF, click the signature field and choose Sign Document.

    The document message bar appears with the compliance status and options.

  5. (Optional) Click View Report in the document message bar (if available) and select each item in the list to show details. When you’re done, close the PDF Signature Report dialog box.
  6. If you’re satisfied with the compliance status of the document, click Sign Document in the document message bar, and add your digital signature.
  7. Save the PDF using a different name than the original, and close the document without making any further changes.

Certify a PDF

When you certify a PDF, you indicate that you approve of its contents. You also specify the types of changes that are permitted for the document to remain certified. For example, suppose that a government agency creates a form with signature fields. When the form is complete, the agency certifies the document, allowing users to change only form fields and sign the document. Users can fill the form and sign the document. However, if they remove pages or add comments, the document doesn’t retain its certified status.

You can apply a certifying signature only if the PDF doesn’t already contain any other signatures. Certifying signatures can be visible or invisible. A blue ribbon icon  in the Signatures panel indicates a valid certifying signature. A digital ID is required to add the certifying digital signature.

  1. Remove content, such as JavaScripts, actions, or embedded media, which may compromise document security.

    To let other Adobe Reader users sign the document, enable usage rights by choosing File > Save As > Reader Extended PDF in Adobe Acrobat.

  2. Choose Tools > Sign & Certify and then select one of the following options. If you don't see the Sign & Certify panel, see the instructions for adding panels at Task panes.
    • With Visible Signature.

    • Without Visible Signature. If you choose this option, your signature appears only in the Signatures panel.

  3. Click OK in the Save As Certified Document dialog box.

    If you are certifying with Visible signatures, you can place the signature in an existing signature field or create a field for the signature. Follow the directions in the prompts to choose a location.

  4. If you’re adding a visible signature, draw the signature field on the page.
    Note: If you enabled View Documents In Preview Document Mode When Signing in the Security Preferences, click Sign Document in the document message bar.
  5. Follow the onscreen instructions to select a digital ID, if prompted.
    Specify a default ID to avoid being prompted each time you sign a PDF.
  6. In the Certify Document dialog box, specify the permitted changes, type your password or PIN for your digital ID, and then click Sign.
    Note: Some digital IDs are configured to ask for a password or other user authentication after you click the Sign button.
  7. Save the PDF using a different filename than the original file, and then close the document without making additional changes. It is a good idea to save it as a different file so that you can retain the original unsigned document.

Timestamp a document

Acrobat X provides users with the capability to add a document timestamp to a PDF without also requiring an identity-based signature. In this way, the authenticity and existence of a document at a particular time can be asserted. These timestamps are compliant with the timestamp and revocation features described in Part 4 of ETSI 102 778 PDF Advanced Electronic Signatures (PAdES) standard. Reader X users can also timestamp a document if the document includes appropriate Reader Enabling features.

For more information on PAdES, see blogs.adobe.com/security/2009/09/eliminating_the_penone_step_at.html

To place a document timestamp:

  1. Open the document to which you want to add a timestamp.
  2. Choose Tools > Sign & Certify > Time Stamp Document. If you don't see the Sign & Certify panel, see the instructions for adding panels at Task panes.
  3. In the Choose Default Timestamp Server dialog box, select a default timestamp server from the list, or add a new default timestamp server.
  4. Click Next, and then save the document with the timestamp.

Remove a digital signature

 Do one of the following:
  • To remove a signature, right-click the signature field and choose Clear Signature.

  • To remove all signatures in a PDF, choose Clear All Signature Fields from the options menu in the Signatures panel.

You cannot remove a signature unless you are the one who placed it and you have the digital ID for signing it installed.

To delete the signature field in Acrobat, choose Tools > Content > Select Object. Then select the signature field and press the Delete key.

Additional resources

For more information on digital signatures, see these resources: