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PDF Document Management 15: Add a Digital Signature into PDF Document

Note: A better way is to add a New Digital Signature Form Field, then, sign the digital signature box inside the latest Adobe Reader.

A digital signature (ID), like a conventional handwritten signature, identifies the person signing a document. Unlike a handwritten signature, a digital signature is difficult to forge because it contains encrypted information that is unique to the signer and easily verified. It is usually password protected and can be stored on your computer in PKCS #12 file format (Personal Information Exchange File, PFX).

When you buy a new digital signature, you get .spc file that contains the certificate and .pvk file that contains your private keys. Use Microsoft command-line tool Pvk2Pfx to convert them into a  PFX file.  See detail here.

The following command generates the .pfx file Mypfxfile.pfx from Mypvkfile.pvk and Myspcfile.spc. The command supplies the password mypassword for the .pvk file, which becomes the password for the .pfx file Mypfxfile.pfx:

pvk2pfx -pvk mypvkfile.pvk -pi mypassword -spc myspcfile.spc -pfx mypfxfile.pfx

This function can create document-level Digital Signature that apply to the entire document.

Here are the steps on how to Add Digital Signature  into PDF Document:

1. Choose Document Menu > Digital Signature

or click Digital Signature Button in the Document Toolbar.

2. Select a PFX file with digital signature.

3. The Create Digital Signature to Document dialog box comes up:


4. Click Close to finish.

Question 1: The Validity of digital signature is displayed as "UNKNOWN" inside Adobe Reader, how to make "Signature Valid"?

1. Click inside the signature with "Validity Unknown";
2. The dialog of "Signature Validity Status" will show up. Click "Signature Properties";
3. From Dialog "Signature Properties", click "Show Signer's Certificate";
4. From Dialog "Certificate Viewer", click "Trust" Tab and then click "Add to Trusted Certificates";
5. "Import Contact Settings" will come up, click OK.
6. Close Adobe Reader and open your PDF again. You will see the "Signature Valid".

Question 2: How to remove the imported digital signature from my computer?

1. Open Adobe Reader=>Edit Menu=>Preferences=>Signatures=>Identities & Trusted Certificates=>More;
2. Dialog "Digital ID and Trusted Certificate Settings" comes up, click "Trusted Certificates". Select the Certificate to remove.
3. From "Internet Explorer" => "Tools" Menu =>Internet Options=>Contents=>Certificates=>Select the Certificate to remove.

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