How to Sign a document using Adobe Acrobat

Before you begin

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A certificate-based signature, like a conventional handwritten signature, identifies the person signing a document. Unlike a handwritten signature, a certificate-based signature is difficult to forge because it contains encrypted information that is unique to the signer. It can be easily verified and informs recipients whether the document was modified after the signer initially signed it.

To sign a document with a certificate-based signature, you must obtain a digital ID or create a self-signed digital ID in Acrobat or Acrobat Reader. The digital ID contains a private key and a certificate with a public key, and more. The private key is used to create the certificate-based signature. The certificate is a credential that is automatically applied to the signed document. The signature is verified when recipients open the document.

When you apply a certificate-based signature, Acrobat uses a hashing algorithm to generate a message digest, which it encrypts using your private key. Acrobat embeds the encrypted message digest in the PDF, certificate details, signature image, and a document version when signed.

Certificate-based signature in a PDF form

Steps to add a certificate-based signature to a PDF

Open a PDF in Acrobat and choose All Tools > more > Use a certificate in the global bar.

Alternatively, from Acrobat Home, select See all tools. In the Protect section, select Use a certificate, and then select a file you want to certify.
The Use a certificate tool is open on the left pane.
- Select Certify (visible signatures) to certify with a visible digital signature, and then select Drag New Signature Rectangle in the dialog box that appears.
- Select Certify (invisible signatures) if you want to certify the document without a visible signature.
Select OK in the Save as Certified Document dialog box.

If you've selected, certify (visible signatures) in step 2, use the mouse to drag and draw a rectangle area where you want your signature to appear.

In the Sign with a Digital ID dialog box, choose the Digital ID you want to use for certifying the document and select Continue, or select Configure New Digital ID to create a new ID.
Select Review to review the document content before signing, then select Sign. Save the PDF when prompted. Your document is now certified.
Certifying and signing documents

The Use a certificate tool lets you apply two types of certificate-based signatures. You can Certify a document, attest to its content or approve a document with the Digitally sign option.

Digitally sign

When you Digitally sign with a certificate, the signature is considered an approval signature.

Certify (visible or invisible signatures)

Certify options provide a higher level of document control than digitally sign. For documents that require certification, you must certify the documents before others sign them. If a document has already been signed, the Certify options are disabled. When you certify a document, you can control the types of changes other people can make. You can certify with or without displaying a signature.

Signatures made with the Certify or Digitally sign options 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 Acrobat Reader provide an option to change the default signing format to a CAdES format. 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. You can change the default signing method or format, in the Signatures panel of the Preferences dialog box. Under Creation & Appearance, click More.
Setting up certificate-based signatures

You can expedite the signing process and optimize your results by making the following preparations in advance.
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 apply a certificate-based signature without a digital id.

Set the default signing method.

Create an appearance for your certificate-based signature. (See Create the signature appearance.)

Use the Preview Document mode to suppress any dynamic content that can alter the appearance of the document and mislead you into signing an unsuitable document. For information about using the Preview Document mode, see Sign in Preview Document mode.

Review all the pages in a document before you sign. Documents can contain signature fields on multiple pages.

Configure the signing application. Both authors and signers should configure their application environment. (See Set signing preferences).

For details on the full range of configuration options in enterprise settings, see the Digital Signatures Guide.

Choose a signature type. Learn about approval and certification signatures to determine the type you should choose to sign your document. (See Signature types.)

Set signing preferences

Signing workflow preferences control what you can see and do when the signing dialog box opens. You can allow certain actions, hide and display data fields, and change how content affects the signing process. Setting signing preferences impacts your ability to see what you are signing. For information on the available signing preferences, see “Signing Workflow Preferences” in the Digital Signature Guide.

Customizing signature workflows using seed values

Seed values offer additional control to document authors by letting them specify which choices signers can make when signing a document. By applying seed values to signature fields in unsigned PDFs, authors can customize options and automate tasks. They can also specify signature requirements for items such as certificates and timestamp servers. For more information about customizing signatures using seed values, see the Digital Signature Guide.
Create the appearance of a certificate-based signature

You determine the look of your certificate-based signature by selecting options in the Signatures panel of the Preferences dialog box. For example, you can include an image of your handwritten signature, a company logo, or a photograph. You can also create different signatures for different purposes. For some, you can provide a greater level of detail.

A signature can also include information that helps others verify your signature, such as the reason for signing, contact information, and more.
Signature format

A. Text signature B. Graphic signature
(Optional) If you want to include an image of your handwritten signature in the certificate-based signature, scan your signature, and save it as an image file. Place the image in a document by itself and convert the document to PDF.

Right-click the signature field and select Sign Document or Certify with Visible Signature
Note: You can also create an appearance using the Signature preferences: Hamburger menu > Preferences > Signatures (Windows) or Acrobat > Preferences > Signatures (macOS).

From the Appearance menu in the Sign dialog box, select Create New Appearance.
In the 'Configure Signature Appearance' dialog box, enter a name for the signature you are creating. This name will be used to select the signature when signing, so choose a brief, descriptive title.

For Configure Graphic, choose an option:

No Graphic

Displays only the default icon and other information specified in the Configure Text section.

Imported Graphic

Displays an image with your certificate-based signature. Select this option to include an image of your handwritten signature. To import the image file, select File, select Browse and then select the image file.

Name

Displays only the default signature icon and your name as it appears in your digital ID file.

For Configure Text, select the options that you want to appear in the signature. Distinguished Name shows the user attributes defined in your digital ID, including your name, organization, and country.

For Text Properties, specify the writing direction and type of digits used, and then click OK. See also Enable right-to-left languages.

(Optional) If the dialog box includes the Additional Signature Information section, specify the reason for signing the document, the location, and your contact information. These options are available only if you set them as your preferences in the Creation and Appearance Preferences dialog box (Preferences > Signatures > Creation & Appearance > More).

Set up a roaming ID account

A roaming ID is a digital ID that is stored on a server and can be accessed by the subscriber. You must have an Internet connection to access a roaming ID and an account from an organization that supplies roaming digital IDs.

Open the Preferences dialog box.

Under Categories, select Signatures.

For Identities & Trusted Certificates, select More.

Expand Digital IDs on the left, select Roaming ID Accounts, and select Add Account.

Type the name and URL for the roaming ID server and select Next.

Type your username and password or follow the directions to create an account. Select Next, and then select Finish.