activePDF Toolkit在安全性方面也提供了極強的加密功能，可以為PDF文件加密，確保文件的安全性，下面貼出的就是為PDF文件加密的代碼示例。

》》》下載activePDF Toolkit試用版

示例代碼如下：

// Copyright (c) 2013 activePDF, Inc.
// Example created 01/27/13

// Make sure to add the activePDF product .NET DLL(s) to your application.
// .NET DLL(s) are typically found in the products 'bin' folder.

class Examples
{
  public void main()
  {
    string strPath;
    int intEncryptFile;
    int intEncryptFile128;
    int intEncryptFileAES;
    
    strPath = AppDomain.CurrentDomain.BaseDirectory;

    // Instantiate Object
    APToolkitNET.Toolkit oTK = new APToolkitNET.Toolkit();
    
    // Toolkit can directly encrypt a PDF file
    // There are 3 types of encryption that Toolkit supports
    // 40-bit, 128-bit and AES
    // !NOTE: Evaluation keys will append 'DEMO' to the start of the password
    
    // To encrypt a file with 40-bit encryption
    intEncryptFile = oTK.EncryptFile(strPath + "PDF.pdf", strPath + "Encrypted-40.pdf", "UserPassword", "OwnerPassword", 1, 1, 0, 0);
    if (intEncryptFile != 0)
    {
      ErrorHandler("EncryptFile", intEncryptFile);
    }
    
    // To encrypt a file with 128-bit encryption
    intEncryptFile128 = oTK.EncryptFile128(strPath + "PDF.pdf", strPath + "Encrypted-128.pdf", "UserPassword", "OwnerPassword", 1, 1, 0, 0, 1, 0, 1, 1);
    if (intEncryptFile128 != 0)
    {
      ErrorHandler("EncryptFile128", intEncryptFile128);
    }
    
    // To encrypt a file with AES encryption
    intEncryptFileAES = oTK.EncryptFileAES(strPath + "PDF.pdf", strPath + "Encrypted-AES.pdf", "UserPassword", "OwnerPassword", 1, 1, 0, 0, 1, 0, 1, 1);
    if (intEncryptFileAES != 0)
    {
      ErrorHandler("EncryptFileAES", intEncryptFileAES);
    }
    
    // Release Object
    oTK = null;
    
    // Process Complete
    System.Diagnostics.Debug.WriteLine("Done!");
  }
  
  // Error Handling
  public static void ErrorHandler(string strMethod, object rtnCode)
  {
    System.Diagnostics.Debug.WriteLine(strMethod + " error:  " + rtnCode.ToString());
  }
}