A Developer's Guide to Digitally Signing PDFs with C#

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

' Create a new PDF from an HTML string for demonstration.
Private renderer = New ChromePdfRenderer()
Private pdf = renderer.RenderHtmlAsPdf("<h1>Signed Document</h1><p>This document has been digitally signed.</p>")

' Load the certificate from a .pfx file with its password.
' The X509KeyStorageFlags.Exportable flag is crucial for allowing the private key to be used in the signing process.
Private cert = New X509Certificate2("IronSoftware.pfx", "123456", X509KeyStorageFlags.Exportable)

' Create a PdfSignature object using the loaded certificate.
Private signature = New PdfSignature(cert)

' Apply the signature to the PDF document.
pdf.Sign(signature)

' Save the securely signed PDF document.
pdf.SaveAs("Signed.pdf")

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

' Create a new PDF from an HTML string for demonstration.
Private renderer = New ChromePdfRenderer()
Private pdf = renderer.RenderHtmlAsPdf("<h1>Signed Document</h1><p>This document has been digitally signed.</p>")

' Load the certificate from a .pfx file with its password.
' The X509KeyStorageFlags.Exportable flag is crucial for allowing the private key to be used in the signing process.
Private cert = New X509Certificate2("IronSoftware.pfx", "123456", X509KeyStorageFlags.Exportable)

' Create a PdfSignature object using the loaded certificate.
Private signature = New PdfSignature(cert)

' Apply the signature to the PDF document.
pdf.Sign(signature)

' Save the securely signed PDF document.
pdf.SaveAs("Signed.pdf")

Imports IronPdf.Signing
Imports IronSoftware.Drawing

' This example demonstrates various ways to add a visual image to a PDF signature.

' Create a PdfSignature object.
Dim signature As New PdfSignature("IronSoftware.pfx", "123456")

' Define the position and size for the signature image on the first page (index 0).
' Rectangle parameters: x position, y position, width, height
Dim signatureRectangle As New Rectangle(350, 750, 200, 100)

' Option 1: Set the SignatureImage property directly.
' This is the most straightforward approach
signature.SignatureImage = New PdfSignatureImage("assets/visual-signature.png", 0, signatureRectangle)

' Option 2: Use the LoadSignatureImageFromFile method.
' This method provides the same functionality with a different syntax
signature.LoadSignatureImageFromFile("assets/visual-signature.png", 0, signatureRectangle)

' Option 3: Load an image from a stream. This is useful for images generated in memory.
' Perfect for scenarios where images are retrieved from databases or web services
Dim image As AnyBitmap = AnyBitmap.FromFile("assets/visual-signature.png")
Using imageStream = image.ToStream()
    signature.LoadSignatureImageFromStream(imageStream, 0, signatureRectangle)
End Using

' After configuring the signature image, apply it to a PDF.
Dim pdf As PdfDocument = PdfDocument.FromFile("invoice.pdf")
pdf.Sign(signature)
pdf.SaveAs("VisualSignature.pdf")

Imports IronPdf.Signing
Imports IronSoftware.Drawing

' This example demonstrates various ways to add a visual image to a PDF signature.

' Create a PdfSignature object.
Dim signature As New PdfSignature("IronSoftware.pfx", "123456")

' Define the position and size for the signature image on the first page (index 0).
' Rectangle parameters: x position, y position, width, height
Dim signatureRectangle As New Rectangle(350, 750, 200, 100)

' Option 1: Set the SignatureImage property directly.
' This is the most straightforward approach
signature.SignatureImage = New PdfSignatureImage("assets/visual-signature.png", 0, signatureRectangle)

' Option 2: Use the LoadSignatureImageFromFile method.
' This method provides the same functionality with a different syntax
signature.LoadSignatureImageFromFile("assets/visual-signature.png", 0, signatureRectangle)

' Option 3: Load an image from a stream. This is useful for images generated in memory.
' Perfect for scenarios where images are retrieved from databases or web services
Dim image As AnyBitmap = AnyBitmap.FromFile("assets/visual-signature.png")
Using imageStream = image.ToStream()
    signature.LoadSignatureImageFromStream(imageStream, 0, signatureRectangle)
End Using

' After configuring the signature image, apply it to a PDF.
Dim pdf As PdfDocument = PdfDocument.FromFile("invoice.pdf")
pdf.Sign(signature)
pdf.SaveAs("VisualSignature.pdf")

Imports System

' Load a PDF with a complex signature history.
Dim pdf = PdfDocument.FromFile("multi_signed_report.pdf")

' Verify all signatures across all revisions.
' This ensures document integrity throughout its entire history
Dim allSignaturesValid As Boolean = pdf.VerifySignatures()
Console.WriteLine($"All signatures are valid: {allSignaturesValid}")

' Roll back to the first revision (index 0).
' Useful for reviewing the original document state
If pdf.RevisionCount > 1 Then
    Dim firstRevision As PdfDocument = pdf.GetRevision(0)
    firstRevision.SaveAs("report_first_revision.pdf")
End If

' Create a completely unsigned version of the document.
' This removes all digital signatures while preserving content
pdf.RemoveSignatures()
pdf.SaveAs("report_unsigned.pdf")

Imports System

' Load a PDF with a complex signature history.
Dim pdf = PdfDocument.FromFile("multi_signed_report.pdf")

' Verify all signatures across all revisions.
' This ensures document integrity throughout its entire history
Dim allSignaturesValid As Boolean = pdf.VerifySignatures()
Console.WriteLine($"All signatures are valid: {allSignaturesValid}")

' Roll back to the first revision (index 0).
' Useful for reviewing the original document state
If pdf.RevisionCount > 1 Then
    Dim firstRevision As PdfDocument = pdf.GetRevision(0)
    firstRevision.SaveAs("report_first_revision.pdf")
End If

' Create a completely unsigned version of the document.
' This removes all digital signatures while preserving content
pdf.RemoveSignatures()
pdf.SaveAs("report_unsigned.pdf")

Imports IronPdf.Editing

' Load the existing PDF document.
Dim pdf = PdfDocument.FromFile("invoice.pdf")

' Create an HtmlStamp containing our signature image.
' HtmlStamp allows us to position HTML content precisely on the page
Dim signatureStamp = New HtmlStamp("<img src='assets/signature.png'/>") With {
    ' Configure the stamp's position and appearance.
    .VerticalAlignment = VerticalAlignment.Bottom,
    .HorizontalAlignment = HorizontalAlignment.Right,
    .Margin = 10,  ' Add some space from the edge.
    .Opacity = 90  ' Make it slightly transparent for a more authentic look.
}

' Apply the stamp to all pages of the PDF.
' You can also specify specific page numbers if needed
pdf.ApplyStamp(signatureStamp)

' Save the modified PDF document.
pdf.SaveAs("official_invoice.pdf")

Imports IronPdf.Editing

' Load the existing PDF document.
Dim pdf = PdfDocument.FromFile("invoice.pdf")

' Create an HtmlStamp containing our signature image.
' HtmlStamp allows us to position HTML content precisely on the page
Dim signatureStamp = New HtmlStamp("<img src='assets/signature.png'/>") With {
    ' Configure the stamp's position and appearance.
    .VerticalAlignment = VerticalAlignment.Bottom,
    .HorizontalAlignment = HorizontalAlignment.Right,
    .Margin = 10,  ' Add some space from the edge.
    .Opacity = 90  ' Make it slightly transparent for a more authentic look.
}

' Apply the stamp to all pages of the PDF.
' You can also specify specific page numbers if needed
pdf.ApplyStamp(signatureStamp)

' Save the modified PDF document.
pdf.SaveAs("official_invoice.pdf")

Imports IronPdf.Forms
Imports IronSoftware.Drawing

' Create a new PDF to add the signature field to.
Dim renderer As New ChromePdfRenderer()
Dim pdf = renderer.RenderHtmlAsPdf("<h1>Please Sign Below</h1>")

' Define the properties for the signature form field.
Dim fieldName As String = "ClientSignature"  ' Unique identifier for the field
Dim pageIndex As Integer = 0  ' Add to the first page (zero-indexed)
Dim fieldRect As New Rectangle(50, 200, 300, 100)  ' Position: (x, y), Size: (width, height)

' Create the SignatureFormField object.
' This creates an interactive field that users can click to sign
Dim signatureField As New SignatureFormField(fieldName, pageIndex, fieldRect)

' Add the signature field to the PDF's form.
pdf.Form.Add(signatureField)

' Save the PDF with the new interactive signature field.
pdf.SaveAs("interactive_signature.pdf")

Imports IronPdf.Forms
Imports IronSoftware.Drawing

' Create a new PDF to add the signature field to.
Dim renderer As New ChromePdfRenderer()
Dim pdf = renderer.RenderHtmlAsPdf("<h1>Please Sign Below</h1>")

' Define the properties for the signature form field.
Dim fieldName As String = "ClientSignature"  ' Unique identifier for the field
Dim pageIndex As Integer = 0  ' Add to the first page (zero-indexed)
Dim fieldRect As New Rectangle(50, 200, 300, 100)  ' Position: (x, y), Size: (width, height)

' Create the SignatureFormField object.
' This creates an interactive field that users can click to sign
Dim signatureField As New SignatureFormField(fieldName, pageIndex, fieldRect)

' Add the signature field to the PDF's form.
pdf.Form.Add(signatureField)

' Save the PDF with the new interactive signature field.
pdf.SaveAs("interactive_signature.pdf")

Imports IronPdf
Imports System

' Import the Signed PDF report
Dim pdf = PdfDocument.FromFile("multi_signed_report.pdf")

' Using GetVerifiedSignatures() obtain a list of `VerifiedSignature` objects from the PDF
pdf.GetVerifiedSignatures().ForEach(Sub(signature)
    ' Print out the SignerName of each `VerifiedSignature` object
    Console.WriteLine($"SignatureName: {signature.SignerName}")
End Sub)

Imports IronPdf
Imports System

' Import the Signed PDF report
Dim pdf = PdfDocument.FromFile("multi_signed_report.pdf")

' Using GetVerifiedSignatures() obtain a list of `VerifiedSignature` objects from the PDF
pdf.GetVerifiedSignatures().ForEach(Sub(signature)
    ' Print out the SignerName of each `VerifiedSignature` object
    Console.WriteLine($"SignatureName: {signature.SignerName}")
End Sub)