Pdf Digitally signing Leave feedback

GroupDocs.Signature provides DigitalSignOptions class to specify different amount of settings for Digital signature

• digital certificate (file on local disk CertificateFilePath or stream CertificateStream) (required)
• password of digital certificate Password (required)
• digital signature details (Reason, Contact, Location)
• signature image as digital signature appearance on document page (ImageFilePath or ImageStream)
• image signature appearance on document page (Alignment, Margin etc.)

Here are the steps to add Digital signature into document with GroupDocs.Signature:

• Create new instance of Signature class and pass source document path as a constructor parameter.
• Instantiate the DigitalSignOptions object with required certificate and its password.
• Call Sign method of  Signature class instance and pass DigitalSignOptions to it.
• Analyze SignResult result to check newly created signatures if needed.

This example shows how to add Digital signature to document. See SignResult

using (Signature signature = new Signature("sample.pdf"))
{
    // initialize digital option with certificate file path
    DigitalSignOptions options = new DigitalSignOptions("certificate.pfx")
    {
        // certifiate password
        Password = "1234567890",
        // digital certificate details
        Reason = "Sign",
        Contact = "JohnSmith",
        Location = "Office1",
        // image as digital certificate appearance on document pages
        ImageFilePath = "sample.jpg",
        //
        AllPages = true,
        Width = 80,
        Height = 60,
        VerticalAlignment = VerticalAlignment.Bottom,
        HorizontalAlignment = HorizontalAlignment.Right,
        Margin = new Padding() {  Bottom = 10, Right = 10},
    };
    signature.Sign("signed.pdf", options);
}

What is Long-Term Validation (LTV) for Digital Signatures?

Long-Term Validation (LTV) is a method used to ensure the continued validity of digital signatures over time, even after the signing certificate expires or is revoked. LTV embeds additional information within the signed document, such as the certificate’s revocation status, timestamp, and the certificate chain, which allows anyone verifying the signature in the future to determine its authenticity, even if the original certificate is no longer available.

Why is LTV Important?

Digital signatures rely on certificates, which have expiration dates. Once the signing certificate expires or is revoked, the signature may no longer be considered valid. However, many legal, financial, and regulatory scenarios require documents to remain valid for years or decades. LTV solves this problem by embedding validation data directly into the signed document, ensuring that the signature’s authenticity can be verified at any point in the future.

Here is an example of how to implement Long-Term Validation (LTV) for a PDF document using GroupDocs.Signature:

using (Signature signature = new Signature("sample.pdf"))
{
    // initialize digital option with certificate file path
    DigitalSignOptions options = new DigitalSignOptions("certificate.pfx")
    {
        // certifiate password
        Password = "1234567890",
        // digital certificate details
        Reason = "Sign",
        Contact = "JohnSmith",
        Location = "Office1",
        AllPages = true,
        Width = 80,
        Height = 60,
        VerticalAlignment = VerticalAlignment.Bottom,
        HorizontalAlignment = HorizontalAlignment.Right,
        Margin = new Padding() {Bottom = 10, Right = 10},
        
        // Enable Long-Term Validation (LTV) to ensure signature validity over time
        UseLtv = true
    };
    signature.Sign("signed.pdf", options);
}

After signing a document with LTV support, you can check whether the signature includes LTV data using Adobe Acrobat. Here is the example of signature detailes in Adobe Acrobat:

You may easily run the code above and see the feature in action in our GitHub examples:

• GroupDocs.Signature for .NET examples, plugins, and showcase
• GroupDocs.Signature for Java examples, plugins, and showcase
• Document Signature for .NET MVC UI Example
• Document Signature for .NET App WebForms UI Example
• Document Signature for Java App Dropwizard UI Example
• Document Signature for Java Spring UI Example

Along with the full-featured .NET library, we provide simple but powerful free online apps.

To sign PDF, Word, Excel, PowerPoint, and other documents you can use the online apps from the GroupDocs.Signature App Product Family.