Updated 1 November 2026C#PDF encryption

This tutorial shows how to encrypt a PDF, apply permissions and check the result from a C# WinForms or console application. The component is registered as PDFEncryptX.EncryptLib and works in both 32-bit and 64-bit processes.

The example uses the vendor's permission mask: printing, copying and editing are disabled while annotations and form filling remain available. Adjust the mask to match your document policy.

Before you start

  1. Install the PDF Encrypt ActiveX DLL trial. The installer registers the COM component.
  2. Add a reference to PDFEncryptX in your project (or use late binding with CreateObject).
  3. Call SetLicenseKey() before converting. During evaluation you can leave the placeholder key.
  4. Load the input PDF, build the permission mask, call Encrypt(), then close the document.

Complete example

C#
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using PDFEncryptX;

namespace Application1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {

            EncryptLibClass obj = new PDFEncryptX.EncryptLibClass();

            obj.SetLicenseKey("License Code");

            int iRtn = obj.LoadFromFile(".\\PDFEncryptX.pdf", "");

            if (iRtn == 1)
            {
                if (obj.IsEncrypted == 1)
                {
                    textBox1.Text = "YES";
                }
                else
                {
                    textBox1.Text = "NO";
                }
                textBox2.Text = obj.PageCount.ToString();
                textBox3.Text = obj.FileSize.ToString();
            }

            //Create Permissions: Can not to print, copy and edit.
            int iPermissions = obj.CreatePermissions(0, 0, 0, 1, 1, 1, 1, 1);

            //Call encrypt method
            int iValue = obj.Encrypt(".\\PDFEncryptX_CanNot_Print_Copy_Edit.pdf", 2, iPermissions, "", "");
            switch(iValue)
            {
                case 0: textBox4.Text = "0->Encrypt failed"; break;
                case 1: textBox4.Text = "1->Encrypt successful"; break;
                case 2: textBox4.Text = "2->Ignore - file already encrypted"; break;
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}

How it works

  • LoadFromFile() returns 1 on success, 0 when the file cannot be loaded, and -1 when the file does not exist.
  • Encrypt() returns 0 for failure, 1 for success and 2 when the file is already encrypted.
  • The output path must be writable by the account running the application.
During evaluation, leave the placeholder license key in place. After purchase, replace it with the key from your email.