How to Read the Signer's Certificate from Verified PDF Signatures in C# (X.509, eIDAS, Chain)

using IronPdf;
using IronPdf.Signing.Inspection;

var pdf = PdfDocument.FromFile("eidas-signed-invoice.pdf");

foreach (var sig in pdf.GetVerifiedSignatures())
{
    var cert = sig.SignerCertificate;
    if (cert is null) continue;

    // Subject DN SERIALNUMBER OID (national ID, tax ID, etc.)
    Console.WriteLine($"Signer Identity (SERIALNUMBER): {cert.SubjectSerialNumber ?? "not present"}");

    // Certificate's own serial from the issuing CA
    Console.WriteLine($"Certificate Serial (CA-issued):  {cert.CertificateSerialNumber}");
}

Imports IronPdf
Imports IronPdf.Signing.Inspection

Dim pdf = PdfDocument.FromFile("eidas-signed-invoice.pdf")

For Each sig In pdf.GetVerifiedSignatures()
    Dim cert = sig.SignerCertificate
    If cert Is Nothing Then Continue For

    ' Subject DN SERIALNUMBER OID (national ID, tax ID, etc.)
    Console.WriteLine($"Signer Identity (SERIALNUMBER): {If(cert.SubjectSerialNumber, "not present")}")

    ' Certificate's own serial from the issuing CA
    Console.WriteLine($"Certificate Serial (CA-issued):  {cert.CertificateSerialNumber}")
Next

using IronPdf;
using IronPdf.Signing.Inspection;

var pdf = PdfDocument.FromFile("archived-contract.pdf");

foreach (var sig in pdf.GetVerifiedSignatures())
{
    var cert = sig.SignerCertificate;
    if (cert is null) continue;

    Console.WriteLine($"Valid from:  {cert.NotBefore}");
    Console.WriteLine($"Valid until: {cert.NotAfter}");
    Console.WriteLine($"Expired now: {cert.IsExpired}");

    // Confirm certificate was valid when the document was signed
    if (sig.SigningDate.HasValue)
    {
        bool validAtSigning = cert.IsValidAt(sig.SigningDate.Value);
        Console.WriteLine($"Valid at signing time ({sig.SigningDate.Value}): {validAtSigning}");
    }
}

Imports IronPdf
Imports IronPdf.Signing.Inspection

Dim pdf = PdfDocument.FromFile("archived-contract.pdf")

For Each sig In pdf.GetVerifiedSignatures()
    Dim cert = sig.SignerCertificate
    If cert Is Nothing Then Continue For

    Console.WriteLine($"Valid from:  {cert.NotBefore}")
    Console.WriteLine($"Valid until: {cert.NotAfter}")
    Console.WriteLine($"Expired now: {cert.IsExpired}")

    ' Confirm certificate was valid when the document was signed
    If sig.SigningDate.HasValue Then
        Dim validAtSigning As Boolean = cert.IsValidAt(sig.SigningDate.Value)
        Console.WriteLine($"Valid at signing time ({sig.SigningDate.Value}): {validAtSigning}")
    End If
Next

using IronPdf;
using IronPdf.Signing.Inspection;
using System.Collections.Generic;

// Known-good signer thumbprints from a compliance database
var pinnedThumbprints = new HashSet<string>
{
    "A1B2C3D4E5F6A1B2C3D4E5F6A1B2C3D4E5F6A1B2C3D4E5F6A1B2C3D4E5F6A1B2",
    "F6E5D4C3B2A1F6E5D4C3B2A1F6E5D4C3B2A1F6E5D4C3B2A1F6E5D4C3B2A1F6E5"
};

var pdf = PdfDocument.FromFile("submitted-form.pdf");

foreach (var sig in pdf.GetVerifiedSignatures())
{
    var cert = sig.SignerCertificate;
    if (cert is null) continue;

    // Pin against trusted thumbprint list
    bool trusted = pinnedThumbprints.Contains(cert.Sha256Thumbprint);
    Console.WriteLine($"Signer: {cert.CommonName}, Thumbprint: {cert.Sha256Thumbprint}");
    Console.WriteLine($"Pinned: {trusted}");
}

Imports IronPdf
Imports IronPdf.Signing.Inspection
Imports System.Collections.Generic

' Known-good signer thumbprints from a compliance database
Dim pinnedThumbprints As New HashSet(Of String) From {
    "A1B2C3D4E5F6A1B2C3D4E5F6A1B2C3D4E5F6A1B2C3D4E5F6A1B2C3D4E5F6A1B2",
    "F6E5D4C3B2A1F6E5D4C3B2A1F6E5D4C3B2A1F6E5D4C3B2A1F6E5D4C3B2A1F6E5"
}

Dim pdf = PdfDocument.FromFile("submitted-form.pdf")

For Each sig In pdf.GetVerifiedSignatures()
    Dim cert = sig.SignerCertificate
    If cert Is Nothing Then Continue For

    ' Pin against trusted thumbprint list
    Dim trusted As Boolean = pinnedThumbprints.Contains(cert.Sha256Thumbprint)
    Console.WriteLine($"Signer: {cert.CommonName}, Thumbprint: {cert.Sha256Thumbprint}")
    Console.WriteLine($"Pinned: {trusted}")
Next

using IronPdf;
using IronPdf.Signing.Inspection;
using System.Security.Cryptography.X509Certificates;

var pdf = PdfDocument.FromFile("signed-report.pdf");

foreach (var sig in pdf.GetVerifiedSignatures())
{
    var cert = sig.SignerCertificate;
    if (cert is null) continue;

    // Construct X509Certificate2 from defensive DER copy
    byte[] derBytes = cert.RawData;
    var x509 = new X509Certificate2(derBytes);

    Console.WriteLine($"X509 Subject:    {x509.Subject}");
    Console.WriteLine($"X509 Issuer:     {x509.Issuer}");
    Console.WriteLine($"X509 Serial:     {x509.SerialNumber}");
    Console.WriteLine($"X509 Algorithm:  {x509.SignatureAlgorithm.FriendlyName}");
    Console.WriteLine($"X509 Key Size:   {x509.PublicKey.Key.KeySize} bits");
}

Imports IronPdf
Imports IronPdf.Signing.Inspection
Imports System.Security.Cryptography.X509Certificates

Dim pdf = PdfDocument.FromFile("signed-report.pdf")

For Each sig In pdf.GetVerifiedSignatures()
    Dim cert = sig.SignerCertificate
    If cert Is Nothing Then Continue For

    ' Construct X509Certificate2 from defensive DER copy
    Dim derBytes As Byte() = cert.RawData
    Dim x509 = New X509Certificate2(derBytes)

    Console.WriteLine($"X509 Subject:    {x509.Subject}")
    Console.WriteLine($"X509 Issuer:     {x509.Issuer}")
    Console.WriteLine($"X509 Serial:     {x509.SerialNumber}")
    Console.WriteLine($"X509 Algorithm:  {x509.SignatureAlgorithm.FriendlyName}")
    Console.WriteLine($"X509 Key Size:   {x509.PublicKey.Key.KeySize} bits")
Next

using IronPdf;
using IronPdf.Signing.Inspection;

var pdf = PdfDocument.FromFile("enterprise-signed.pdf");

foreach (var sig in pdf.GetVerifiedSignatures())
{
    Console.WriteLine($"--- Signature: {sig.SignatureName} ---");
    Console.WriteLine($"Chain length: {sig.CertificateChain.Count}");

    // Walk from signer (index 0) through intermediates to root CA
    for (int i = 0; i < sig.CertificateChain.Count; i++)
    {
        var cert = sig.CertificateChain[i];
        string role = i == 0 ? "Signer"
                    : i == sig.CertificateChain.Count - 1 ? "Root CA"
                    : $"Intermediate CA ({i})";

        Console.WriteLine($"  [{role}]");
        Console.WriteLine($"    Subject:     {cert.SubjectDN}");
        Console.WriteLine($"    Issuer:      {cert.IssuerDN}");
        Console.WriteLine($"    Serial:      {cert.CertificateSerialNumber}");
        Console.WriteLine($"    Valid:       {cert.NotBefore} to {cert.NotAfter}");
        Console.WriteLine($"    Expired:     {cert.IsExpired}");
        Console.WriteLine($"    Thumbprint:  {cert.Sha256Thumbprint}");
    }
}

Imports IronPdf
Imports IronPdf.Signing.Inspection

Dim pdf = PdfDocument.FromFile("enterprise-signed.pdf")

For Each sig In pdf.GetVerifiedSignatures()
    Console.WriteLine($"--- Signature: {sig.SignatureName} ---")
    Console.WriteLine($"Chain length: {sig.CertificateChain.Count}")

    ' Walk from signer (index 0) through intermediates to root CA
    For i As Integer = 0 To sig.CertificateChain.Count - 1
        Dim cert = sig.CertificateChain(i)
        Dim role As String = If(i = 0, "Signer", If(i = sig.CertificateChain.Count - 1, "Root CA", $"Intermediate CA ({i})"))

        Console.WriteLine($"  [{role}]")
        Console.WriteLine($"    Subject:     {cert.SubjectDN}")
        Console.WriteLine($"    Issuer:      {cert.IssuerDN}")
        Console.WriteLine($"    Serial:      {cert.CertificateSerialNumber}")
        Console.WriteLine($"    Valid:       {cert.NotBefore} to {cert.NotAfter}")
        Console.WriteLine($"    Expired:     {cert.IsExpired}")
        Console.WriteLine($"    Thumbprint:  {cert.Sha256Thumbprint}")
    Next
Next