How To Secure PDF Files in C#

Updated:August 6, 2025

Introduction

For developers working with private, sensitive, or confidential PDF documents, PDF security is a crucial aspect to consider. IronPDF is designed to empower developers with a library that handles PDF security effortlessly and without lengthy learning curves. With IronPDF, you can easily sign PDF documents to ensure authenticity, create custom permissions that control how people interact with your documents, fill out PDF forms, and more-all in a practical, efficient manner.

So, if you're looking for a tool that can handle everything from PDF signing to editing PDF forms, then IronPDF is the tool for you. With an easy-to-implement API, you can have IronPDF up and running in your C# applications in no time. It enables you to create readable code that can handle PDF security in just a few lines, eliminating the need for complex, hard-to-understand code files and alleviating the burden.

In this tutorial, we will start by introducing IronPDF's comprehensive set of PDF security features. Next, we will explore some code examples that demonstrate these tools in action. By the end of our time together today, you will be able to create secure PDF documents with ease using IronPDF. So, let's dive in!

Ensure Authenticity
PDF Form Management
- Create PDF Forms
- Fill out and Edit PDF Forms
Secure Your PDF Documents
- Sanitize PDF Documents
- Set PDF Passwords and Permissions

Start using IronPDF in your project today with a free trial.

First Step:

Install with NuGet

Check out IronPDF on NuGet for quick installation. With over 10 million downloads, it’s transforming PDF development with C#. You can also download the DLL or Windows installer.

Ensure Authenticity

Often, when working with PDFs, developers and companies need to ensure the authenticity of the document. There are numerous reasons for ensuring the authenticity of a PDF, ranging from compliance with legal and regulatory standards to long-term archiving and even situations such as digital forensics. Regardless of the reason, IronPDF offers a seamless method for applying digital signatures to PDF files and authenticating revision histories.

Signing PDFs

IronPDF simplifies the process of signing PDF documents programmatically, offering concise methods and multiple approaches tailored to your specific needs. These approaches are designed to be straightforward and user-friendly, empowering you to sign PDFs with confidence.

Digitally signing a PDF with a Certificate.
Adding a graphical signature to an existing PDF.
Stamping a certificate image onto a PDF.
Adding a blank signature field to the PDF for viewers to sign.

For this example, let's examine how to sign a PDF with a digital signature.

:path=/static-assets/pdf/content-code-examples/how-to/signing-X509Certificate2-with-privatekey.cs

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

ChromePdfRenderer renderer = new ChromePdfRenderer();
PdfDocument pdf = renderer.RenderHtmlAsPdf("<h1>foo</h1>");

// Create X509Certificate2 object with X509KeyStorageFlags set to Exportable
X509Certificate2 cert = new X509Certificate2("IronSoftware.pfx", "123456", X509KeyStorageFlags.Exportable);

// Create PdfSignature object
var sig = new PdfSignature(cert);

// Sign PDF document
pdf.Sign(sig);

pdf.SaveAs("signed.pdf");

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

Private renderer As New ChromePdfRenderer()
Private pdf As PdfDocument = renderer.RenderHtmlAsPdf("<h1>foo</h1>")

' Create X509Certificate2 object with X509KeyStorageFlags set to Exportable
Private cert As New X509Certificate2("IronSoftware.pfx", "123456", X509KeyStorageFlags.Exportable)

' Create PdfSignature object
Private sig = New PdfSignature(cert)

' Sign PDF document
pdf.Sign(sig)

pdf.SaveAs("signed.pdf")

$vbLabelText $csharpLabel

Visit the how-to guide to learn more about IronPDF's signing capabilities and to see the other methods in action.

Set & Edit Metadata

When we discuss metadata for PDF documents, we're referring to vital information about the PDF itself, such as the Author, the date it was created, keywords, copyright information, and more. The security of this metadata is of utmost importance, as it can contain sensitive information that must be protected from exploitation or revelation by unauthorized individuals.

With IronPDF, you can easily edit your PDF's metadata to ensure it doesn't contain any sensitive information. Another method could be to encrypt your PDF to prevent unauthorized access; however, we'll explore PDF encryption further later in the article. Beyond fundamental security concerns, there are numerous benefits to utilizing PDF metadata. By doing so, you can enhance database searchability, increase internet searchability, and inspire new ways of using and interacting with PDF documents.

By setting up custom metadata, such as the keywords field, you can easily inform readers about the information they can expect to find in your PDF and ensure it appears in related searches.

:path=/static-assets/pdf/content-code-examples/how-to/metadata-set-edit.cs

using IronPdf;
using System;

ChromePdfRenderer renderer = new ChromePdfRenderer();
PdfDocument pdf = renderer.RenderHtmlAsPdf("<h1>Metadata</h1>");

// Access the MetaData class and set the pre-defined metadata properties.
pdf.MetaData.Author = "Iron Software";
pdf.MetaData.CreationDate = DateTime.Today;
pdf.MetaData.Creator = "IronPDF";
pdf.MetaData.Keywords = "ironsoftware,ironpdf,pdf";
pdf.MetaData.ModifiedDate = DateTime.Now;
pdf.MetaData.Producer = "IronPDF";
pdf.MetaData.Subject = "Metadata Tutorial";
pdf.MetaData.Title = "IronPDF Metadata Tutorial";

pdf.SaveAs("pdf-with-metadata.pdf");

IRON VB CONVERTER ERROR developers@ironsoftware.com

$vbLabelText $csharpLabel

For a more detailed explanation of this code snippet and to explore its additional functionality, please refer to our comprehensive how-to guide.

Edit & Sign Revision History

When working with PDF files, the revision history is a crucial feature that allows you to revert to previous versions of your document and track and manage changes made to a PDF document over time. With IronPDF, you can easily manage the PDF revision history, see who has made changes when working in a collaborative environment, and sign the revision history of a PDF to ensure authenticity.

:path=/static-assets/pdf/content-code-examples/how-to/signing-revision.cs

using IronPdf;
using IronPdf.Rendering;

// Import PDF and enable TrackChanges
PdfDocument pdf = PdfDocument.FromFile("annual_census.pdf", TrackChanges: ChangeTrackingModes.EnableChangeTracking);
// ... various edits ...
pdf.SignWithFile("/assets/IronSignature.p12", "password", null, IronPdf.Signing.SignaturePermissions.AdditionalSignaturesAndFormFillingAllowed);

PdfDocument pdfWithRevision = pdf.SaveAsRevision();

pdfWithRevision.SaveAs("annual_census_2.pdf");

Imports IronPdf
Imports IronPdf.Rendering

' Import PDF and enable TrackChanges
Private pdf As PdfDocument = PdfDocument.FromFile("annual_census.pdf", TrackChanges:= ChangeTrackingModes.EnableChangeTracking)
' ... various edits ...
pdf.SignWithFile("/assets/IronSignature.p12", "password", Nothing, IronPdf.Signing.SignaturePermissions.AdditionalSignaturesAndFormFillingAllowed)

Dim pdfWithRevision As PdfDocument = pdf.SaveAsRevision()

pdfWithRevision.SaveAs("annual_census_2.pdf")

$vbLabelText $csharpLabel

For a more detailed explanation of this code snippet and to explore its additional functionality, please refer to our comprehensive how-to guide.

PDF Form Management

From applications to surveys, there are many reasons why you want to work with PDF forms. IronPDF offers a comprehensive PDF form process, encompassing everything from creating new forms to editing PDF forms and flattening form fields to prevent further edits. With IronPDF, you're well-equipped to handle all your form management needs.

Create PDF Forms

Adding custom forms to your PDF documents is a breeze with IronPDF's easy-to-learn API. Our form tool supports a wide range of form elements, including radio buttons, checkboxes, text areas, input fields, and more. For those looking to create forms that require signatures from those who fill them out, IronPDF supports the use of adding blank signature fields to the form.

By creating dynamic forms with IronPDF, you can ensure that the forms meet your needs and have full control over the entire design process.

:path=/static-assets/pdf/content-code-examples/how-to/create-forms-input-textarea.cs

using IronPdf;

// Input and Text Area forms HTML
string FormHtml = @"
<html>
    <body>
        <h2>Editable PDF Form</h2>
        <form>
            First name: <br> <input type='text' name='firstname' value=''> <br>
            Last name: <br> <input type='text' name='lastname' value=''> <br>
            Address: <br> <textarea name='address' rows='4' cols='50'></textarea>
        </form>
    </body>
</html>
";

// Instantiate Renderer
ChromePdfRenderer Renderer = new ChromePdfRenderer();
Renderer.RenderingOptions.CreatePdfFormsFromHtml = true;

Renderer.RenderHtmlAsPdf(FormHtml).SaveAs("textAreaAndInputForm.pdf");

Imports IronPdf

' Input and Text Area forms HTML
Private FormHtml As String = "
<html>
    <body>
        <h2>Editable PDF Form</h2>
        <form>
            First name: <br> <input type='text' name='firstname' value=''> <br>
            Last name: <br> <input type='text' name='lastname' value=''> <br>
            Address: <br> <textarea name='address' rows='4' cols='50'></textarea>
        </form>
    </body>
</html>
"

' Instantiate Renderer
Private Renderer As New ChromePdfRenderer()
Renderer.RenderingOptions.CreatePdfFormsFromHtml = True

Renderer.RenderHtmlAsPdf(FormHtml).SaveAs("textAreaAndInputForm.pdf")

$vbLabelText $csharpLabel

If you want to learn more about how you can create custom PDF forms with IronPDF and what elements it supports, be sure to check this guide out.

Fill & Edit PDF Forms

With IronPDF, you can automate the PDF signing process by programmatically filling out forms with dynamic data. Whether it's from user input, a connected database, or any other method, IronPDF makes it easy. You can also use it to edit pre-existing forms to better suit your needs.

:path=/static-assets/pdf/content-code-examples/how-to/edit-forms-input-textarea.cs

using IronPdf;

PdfDocument pdf = PdfDocument.FromFile("textAreaAndInputForm.pdf");

// Set text input form values
pdf.Form.FindFormField("firstname").Value = "John";
pdf.Form.FindFormField("lastname").Value = "Smith";

// Set text area form values
pdf.Form.FindFormField("address").Value = "Iron Software LLC\r\n205 N. Michigan Ave.";

pdf.SaveAs("textAreaAndInputFormEdited.pdf");

Imports Microsoft.VisualBasic
Imports IronPdf

Private pdf As PdfDocument = PdfDocument.FromFile("textAreaAndInputForm.pdf")

' Set text input form values
pdf.Form.FindFormField("firstname").Value = "John"
pdf.Form.FindFormField("lastname").Value = "Smith"

' Set text area form values
pdf.Form.FindFormField("address").Value = "Iron Software LLC" & vbCrLf & "205 N. Michigan Ave."

pdf.SaveAs("textAreaAndInputFormEdited.pdf")

$vbLabelText $csharpLabel

For a more detailed explanation of this code snippet and to explore its additional functionality, please refer to our comprehensive how-to guide.

Document Safety

Keeping your PDF documents secure is an essential step when working with private PDF documents, such as those containing sensitive or confidential information. By implementing PDF security features, such as encryption and permission settings, you can ensure that only authorized individuals can access the PDF document.

Sanitize PDF Documents

IronPDF makes the process of sanitizing PDF documents a breeze with its 'cleaner' class. This feature removes any hidden data and metadata that may contain sensitive or private information you don't want to share. To sanitize a PDF document, IronPDF will first convert the PDF document into an image file type, then convert it back into PDF format, now clean of any private data.

:path=/static-assets/pdf/content-code-examples/how-to/sanitize-pdf-sanitize-pdf.cs

using IronPdf;

// Import PDF document
PdfDocument pdf = PdfDocument.FromFile("sample.pdf");

// Sanitize with Bitmap
PdfDocument sanitizeWithBitmap = Cleaner.SanitizeWithBitmap(pdf);

// Sanitize with SVG
PdfDocument sanitizeWithSvg = Cleaner.SanitizeWithSvg(pdf);

// Export PDFs
sanitizeWithBitmap.SaveAs("sanitizeWithBitmap.pdf");
sanitizeWithSvg.SaveAs("sanitizeWithSvg.pdf");

Imports IronPdf

' Import PDF document
Private pdf As PdfDocument = PdfDocument.FromFile("sample.pdf")

' Sanitize with Bitmap
Private sanitizeWithBitmap As PdfDocument = Cleaner.SanitizeWithBitmap(pdf)

' Sanitize with SVG
Private sanitizeWithSvg As PdfDocument = Cleaner.SanitizeWithSvg(pdf)

' Export PDFs
sanitizeWithBitmap.SaveAs("sanitizeWithBitmap.pdf")
sanitizeWithSvg.SaveAs("sanitizeWithSvg.pdf")

$vbLabelText $csharpLabel

Want to learn more about IronPDF's sanitizing methods? Be sure to check out the how-to guide on this topic!

Set PDF Passwords and Permissions

By setting up passwords for your PDFs to restrict access and customizing the permissions for user interaction, you can ensure that only authorized individuals can view your PDF documents.

IronPDF's encryption process encrypts your PDF documents using 128-bit encryption, providing you with full control over permissions to determine whether users can edit, print, annotate, or perform other tasks on the PDF.

:path=/static-assets/pdf/content-code-examples/how-to/pdf-permissions-passwords-add-password.cs

using IronPdf;

ChromePdfRenderer renderer = new ChromePdfRenderer();

PdfDocument pdf = renderer.RenderHtmlAsPdf("<h1>Secret Information:</h1> Hello World");

// Password to edit the pdf
pdf.SecuritySettings.OwnerPassword = "123password";

// Password to open the pdf
pdf.SecuritySettings.UserPassword = "password123";

pdf.SaveAs("protected.pdf");

Imports IronPdf

Private renderer As New ChromePdfRenderer()

Private pdf As PdfDocument = renderer.RenderHtmlAsPdf("<h1>Secret Information:</h1> Hello World")

' Password to edit the pdf
pdf.SecuritySettings.OwnerPassword = "123password"

' Password to open the pdf
pdf.SecuritySettings.UserPassword = "password123"

pdf.SaveAs("protected.pdf")

$vbLabelText $csharpLabel

By following the various methods we've examined today, you can create secure PDF documents with just a few lines of code, making the process straightforward.

For a more detailed explanation of this code snippet and to explore its additional functionality, please refer to our comprehensive how-to guide.

Conclusion

In conclusion, IronPDF plays a vital role in enhancing the signing and security aspects of PDF documents. By utilizing its sanitizing features, users can easily remove sensitive metadata, ensuring that only essential information is shared. Additionally, IronPDF’s robust encryption capabilities enable the implementation of strong password protection and customizable permissions, empowering document owners to control access and interactions with their PDFs. This combination of security measures ensures that confidential information remains protected while also facilitating the safe sharing and signing of important documents. With just a few lines of code, IronPDF simplifies the process of creating secure PDFs, making it an invaluable tool for anyone managing sensitive content and instilling a sense of ease and confidence in the process.

If you would like to make a feature request or have any general questions about IronPDF or licensing, please contact our support team. We will be more than happy to assist you.

Kye Stuart

Chat with engineering team now

Technical Writer

Kye Stuart merges coding passion and writing skill at Iron Software. Educated at Yoobee College in software deployment, they now transform complex tech concepts into clear educational content. Kye values lifelong learning and embraces new tech challenges.

Outside work, they enjoy PC gaming, streaming on Twitch, and ...Read More

Customer Highlight:

Developer Spotlight:

Webinars:

On This Page

How To Secure PDF Files in C#

Introduction

Table of Contents

Ensure Authenticity

Signing PDFs

Set & Edit Metadata

Edit & Sign Revision History

PDF Form Management

Create PDF Forms

Fill & Edit PDF Forms

Document Safety

Sanitize PDF Documents

Set PDF Passwords and Permissions

Conclusion

Ready to Get Started?

Start Free 30 Day Trial

On This Page

How To Secure PDF Files in C#

Introduction

Table of Contents

Ensure Authenticity

Signing PDFs

Set & Edit Metadata

Edit & Sign Revision History

PDF Form Management

Create PDF Forms

Fill & Edit PDF Forms

Document Safety

Sanitize PDF Documents

Set PDF Passwords and Permissions

Conclusion

Ready to Get Started?

Next step: Start free 30-day Trial

Next step: Start free 30-day Trial

Trusted by Over 2 Million Engineers Worldwide