How to secure PDF file with passwords
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 create secured PDF programmatically:
- Create a new C# console application project.
- Install the Syncfusion.Pdf.WinForms NuGet package as reference to your .NET Framework application from NuGet.org.
- Include the following namespace 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
- Use the following code snippet to create secured PDF and encrypt it with both owner and user passwords.
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. 
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 secure PDF file with passwords.
Starting with v16.2.0.x, if you reference Syncfusion assemblies from trial setup or from the NuGet feed, include a license key in your projects. Refer to link to learn about generating and registering Syncfusion license key in your application to use the components without trail message.
