iTextSharp密码保护的PDF

using System;
using System.IO;
using iTextSharp.text.pdf;

namespace iTextSharpExample
{
    class Program
    {
        static void Main(string[] args)
        {
            string inputFile = "input.pdf";
            string outputFile = "output.pdf";
            string userPassword = "userpassword";
            string ownerPassword = "ownerpassword";

            using (PdfReader pdfReader = new PdfReader(inputFile))
            {
                using (PdfStamper pdfStamper = new PdfStamper(pdfReader, new FileStream(outputFile, FileMode.Create)))
                {
                    pdfStamper.SetEncryption(PdfWriter.ENCRYPTION_AES_128, userPassword, ownerPassword, PdfWriter.ALLOW_PRINTING);
                }
            }
        }
    }
}