x509certificate2 can be used to get important information about an existing certificate (valid dates, issuer, etc.). IronPDF allows you to digitally sign a PDF using C#. You can create a new document or sign an existing PDF file. It requires just a single line of code, as illustrated in the simple steps below.

Step 1

1. Get IronPDF

First, install IronPDF to your Visual Studio project. Get it in whichever way is easier for you, either from DLL download or on the NuGet website. Access the C# Library in Visual Studio and let's add a signature.

Install-Package IronPdf

How to Tutorial

2. Understanding Digital Signatures

A Digital Signature is like an electronic driver's license or passport that proves your identity. A digital ID typically contains your name and email address, the name of the organization that issued it, a serial number, and an expiration date. Digital IDs are used for certificate security and digital signatures. This will need to be created with Adobe Acrobat for it to work.

3. Digitally Sign a PDF

Now, let's see the steps for creating an x509certificate2 to digitally sign a PDF using C#.

Today, the IronPDF library offers a simple way to apply signatures, saving time and effort with just a single line of code. You can use it for free during development to test your work. Then, decide on your project. Will you be creating a new document or signing an existing PDF?

In the code example below, a C# form is used to allow the user to select their desired PDF, which can receive a digital signature with a single click.

A .pfx file (Personal Information Exchange Format) should be prepared, which is used to transfer a certificate with the help of a private key.

The SignPdfFile(FileName) method from the PdfSignature class is the main method for a digital signature. Simply select the desired file.

using System.Drawing;
using System.Windows.Forms;
using IronPdf;

namespace DigitalSign
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent(); 
        }

        private void button1_Click(object sender, System.EventArgs e)
        {
            // Open a dialog to select the desired PDF file
            if (openFileDialog1.ShowDialog() == DialogResult.OK)
            {
                textBox1.Text = openFileDialog1.FileName; // Display selected PDF path in the textbox
            }
        }

        private void button2_Click(object sender, System.EventArgs e)
        {
            // Use PdfSignature method to digitally sign the selected PDF
            new PdfSignature("Ironpdf.pfx", "123456").SignPdfFile(textBox1.Text);

            // Provide user feedback that signing is complete
            label3.Text = "Completed!";
            label3.BackColor = Color.LightGreen;
            label3.ForeColor = Color.Black;
        }
    }
}

using System.Drawing;
using System.Windows.Forms;
using IronPdf;

namespace DigitalSign
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent(); 
        }

        private void button1_Click(object sender, System.EventArgs e)
        {
            // Open a dialog to select the desired PDF file
            if (openFileDialog1.ShowDialog() == DialogResult.OK)
            {
                textBox1.Text = openFileDialog1.FileName; // Display selected PDF path in the textbox
            }
        }

        private void button2_Click(object sender, System.EventArgs e)
        {
            // Use PdfSignature method to digitally sign the selected PDF
            new PdfSignature("Ironpdf.pfx", "123456").SignPdfFile(textBox1.Text);

            // Provide user feedback that signing is complete
            label3.Text = "Completed!";
            label3.BackColor = Color.LightGreen;
            label3.ForeColor = Color.Black;
        }
    }
}

Imports System.Drawing
Imports System.Windows.Forms
Imports IronPdf

Namespace DigitalSign
	Partial Public Class Form1
		Inherits Form

		Public Sub New()
			InitializeComponent()
		End Sub

		Private Sub button1_Click(ByVal sender As Object, ByVal e As System.EventArgs)
			' Open a dialog to select the desired PDF file
			If openFileDialog1.ShowDialog() = System.Windows.Forms.DialogResult.OK Then
				textBox1.Text = openFileDialog1.FileName ' Display selected PDF path in the textbox
			End If
		End Sub

		Private Sub button2_Click(ByVal sender As Object, ByVal e As System.EventArgs)
			' Use PdfSignature method to digitally sign the selected PDF
			Call (New PdfSignature("Ironpdf.pfx", "123456")).SignPdfFile(textBox1.Text)

			' Provide user feedback that signing is complete
			label3.Text = "Completed!"
			label3.BackColor = Color.LightGreen
			label3.ForeColor = Color.Black
		End Sub
	End Class
End Namespace

Imports System.Drawing
Imports System.Windows.Forms
Imports IronPdf

Namespace DigitalSign
	Partial Public Class Form1
		Inherits Form

		Public Sub New()
			InitializeComponent()
		End Sub

		Private Sub button1_Click(ByVal sender As Object, ByVal e As System.EventArgs)
			' Open a dialog to select the desired PDF file
			If openFileDialog1.ShowDialog() = System.Windows.Forms.DialogResult.OK Then
				textBox1.Text = openFileDialog1.FileName ' Display selected PDF path in the textbox
			End If
		End Sub

		Private Sub button2_Click(ByVal sender As Object, ByVal e As System.EventArgs)
			' Use PdfSignature method to digitally sign the selected PDF
			Call (New PdfSignature("Ironpdf.pfx", "123456")).SignPdfFile(textBox1.Text)

			' Provide user feedback that signing is complete
			label3.Text = "Completed!"
			label3.BackColor = Color.LightGreen
			label3.ForeColor = Color.Black
		End Sub
	End Class
End Namespace

The above C# code represents a Windows Form application, where:

• A button is used to open a file dialog for selecting a PDF file.
• A second button triggers the signing of the selected PDF using a predefined .pfx file and password.
• Labels are updated to confirm the completion of the signing process.

4. Review Document Signature

As you can see in the output below, as long as a PDF file is selected and the Import Signature button is clicked, it successfully digitally signs the document. With IronPDF, it only took a single line of code.

IronPDF is the perfect tool for PDF-related tasks using C#. IronPDF offers developers methods to render PDF documents into images and extract text and content from a PDF. Additionally, IronPDF is capable of rendering charts in PDFs, adding barcodes using the IronBarcode library, enhancing security with passwords, watermarking, and even handling PDF forms programmatically.

Library Quick Access

API Reference

Read the IronPDF documentation and full list of functions.

API Reference