This concise tutorial shows you how to protect a PDF file with a password in C#. By following the step‑by‑step instructions and using the supplied sample code—just a few API calls—you can quickly implement C# PDF password protection. The guide also lets you pick the encryption algorithm (RC4 or AES) and select either 128‑bit or 256‑bit keys, giving you flexible security options to match your requirements.

Steps to Protect PDF File with Password in C#

1. Add the reference to Conholdate.Total for .NET library in the project for protecting a PDF file
2. Load the input PDF file with confidential data using the Document class
3. Encrypt the PDF file while specifying a password and required parameters for the Encrypt method
4. Save the password-protected PDF file after encrypting it

This guide clearly outlines the method to C# password protect PDF files to safeguard confidential or sensitive information against unauthorized access. It succinctly covers the process: loading the source PDF file, encrypting it with personalized settings, and then saving the modified file to the disk. Furthermore, it enables the selection of the document’s security level. For example, implementing a user password necessitates entering the password each time the PDF is accessed, while a permissions password is only needed for alterations to the PDF’s contents.

Code to Create Password Protected PDF File in C#

The password‑protect‑PDF C# sample shown above delivers a dependable way to lock down your PDF files. With it you can fine‑tune access—allowing or blocking content extraction and annotations—and you can set specific document rights such as printing, form‑filling, and copying. In short, this code gives you full control to safeguard the data in your PDFs.

In this guide we’ve walked through how to create a password‑protected PDF file in C#. If you’d like to take the next step and learn how to sign a PDF document with a QR code, be sure to read our related article: how to sign PDF document with qr code in C#.