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How to protect a PDF with the password using C# and VB.NET?

5 mins read

Syncfusion Essential PDF is a .NET PDF library used to create, read, and edit PDF documents. Using this library, you can protect the PDF document using encryption and set permission to the PDF document operations like printing, editing, and copy content in C# and VB.NET. The Essential PDF supports basic to advanced encryption standards:

  • RC4 (Rivest Cipher 4) 40-bit
  • RC4 128-bit
  • AES 128-bit
  • AES 256-bit Revision 5
  • AES 256-bit Revision 6 (PDF 2.0)

 Steps to protect PDF with password programmatically:

  1. Create a new C# console application project. create project to password protect pdf c# in WinForms PDF
  2. Install the Syncfusion.Pdf.WinForms NuGet package as reference to your .NET Framework application from NuGet.org. NuGet package reference to work for password protect pdf c# in WinForms PDF
  3. Include the following namespaces in the Program.cs file.

C#

using Syncfusion.Pdf;
using Syncfusion.Pdf.Graphics;
using Syncfusion.Pdf.Security;
using System.Drawing;

 

VB.NET

Imports Syncfusion.Pdf
Imports Syncfusion.Pdf.Graphics
Imports Syncfusion.Pdf.Security
Imports System.Drawing

 

  1. Use the following code snippet to protect PDF with password.

C#

//Create PDF document
PdfDocument document = new PdfDocument();
//Add a page in the PDF document
PdfPage page = document.Pages.Add();
//Access the PDF graphics instance of the page
PdfGraphics graphics = page.Graphics;
//Create the PDF font instance
PdfStandardFont font = new PdfStandardFont(PdfFontFamily.TimesRoman, 20f, PdfFontStyle.Bold);
//PDF document security
PdfSecurity security = document.Security;
//Specifies encryption key size, algorithm, and permission
security.KeySize = PdfEncryptionKeySize.Key256BitRevision6;
security.Algorithm = PdfEncryptionAlgorithm.AES;
//Customize permission in the document
security.Permissions = PdfPermissionsFlags.Print | PdfPermissionsFlags.FullQualityPrint;
//Provide owner and user password
security.OwnerPassword = "SyncOPÜ256PDF";
security.UserPassword = "SyncUP€99PDF";
//Draw text in PDF page
graphics.DrawString("Document is encrypted with AES 256 Revision 6", font, PdfBrushes.Black, PointF.Empty);
//Save the document to file system
document.Save("EncryptedDocument.pdf");
//Close the document
document.Close(true);
//This will open the PDF file so, the result will be seen in default PDF viewer
Process.Start("EncryptedDocument.pdf");

 

VB.NET

'Create PDF document
Dim document As New PdfDocument()
'Add a page in the PDF document
Dim page As PdfPage = document.Pages.Add()
'Access the PDF graphics instance of the page
Dim graphics As PdfGraphics = page.Graphics
'Create the PDF font instance
Dim font As New PdfStandardFont(PdfFontFamily.TimesRoman, 20.0F, PdfFontStyle.Bold)
'PDF document security
Dim security As PdfSecurity = document.Security
'Specifies encryption key size, algorithm, and permission
security.KeySize = PdfEncryptionKeySize.Key256BitRevision6
security.Algorithm = PdfEncryptionAlgorithm.AES
'Customize permission in the document
security.Permissions = PdfPermissionsFlags.Print Or PdfPermissionsFlags.FullQualityPrint
'Provide owner and user password
security.OwnerPassword = "SyncOPÜ256PDF"
security.UserPassword = "SyncUP€99PDF"
'Draw text in PDF page
graphics.DrawString("Document is encrypted with AES 256 Revision 6", font, PdfBrushes.Black, PointF.Empty)
'Save the document to file system
document.Save("EncryptedDocument.pdf")
'Close the document
document.Close(True)
'This will open the PDF file so, the result will be seen in default PDF viewer
Process.Start("EncryptedDocument.pdf")

 

Download the work sample from CreateSecurePDFSample.Zip.

By executing the program, you will get the PDF document’s security settings as follows.

c# password protected WinForms PDF

Take a moment to peruse the documentation, where you can  find other options like protect an existing PDF document, change the password, change the permission, remove the password of the PDF document and the features like digitally sign a PDF file, and adding a timestamp in digital signature, with code examples.

Refer here to explore the rich set of Syncfusion Essential PDF features.

An online sample link to protect PDF file with passwords using c#


Note:

Starting with v16.2.0.x, if you reference Syncfusion® assemblies from the trial setup or the NuGet feed, include a license key in your projects. Refer to the link to learn about generating and registering the Syncfusion® license key in your application to use the components without a trial message.

 

Conclusion:

I hope you enjoyed learning about how to protect a PDF with the password using C# and VB.NET.

 

You can refer to our Flutter PDF feature tour page to learn about its other groundbreaking features and documentation, and how to quickly get started with configuration specifications. You can also explore our Flutter PDF Flutter PDF examples to understand how to create and manipulate data.

For current customers, you can check out our components from the License and Downloads page. If you are new to Syncfusion®, you can try our 30-day free trial to explore our other controls.

If you have any queries or require clarifications, please let us know in the comments section below. You can also contact us through our support forums or feedback portal. We are always happy to assist you!

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