Protecting a PDF file with Password

using System.IO;

using iTextSharp.text.pdf;

using System.Diagnostics;

//---- for this itextsharp.dll is required.

protected void Page_Load(object sender, EventArgs e)

    {

        string PDFPath = @"c:\>.netProjects\AllParticipantList.pdf";

        string Password = "abc123";

        EncryptPDFwithPassword(PDFPath, Password); //Password Protecting the pdf

        DecryptPasswordprotectedPDF(PDFPath, Password);

       

    }

private void EncryptPDFwithPassword(string strPDFPath, string strPassword)

    {

        try

       {

           Stream input = new FileStream(strPDFPath, FileMode.Open, FileAccess.Read, FileShare.Read);

            byte[] btSourceFile = StreamToByteArray(input);

            input.Close();

           

            using (Stream output = new FileStream(strPDFPath, FileMode.Create, FileAccess.Write, FileShare.None))

            {

                PdfReader reader = new PdfReader(btSourceFile);

                reader.Close();

                PdfEncryptor.Encrypt(reader, output, true, strPassword, strPassword, PdfWriter.ALLOW_PRINTING);

            }

        }

        catch(Exception ex)

        {

        }

    }

static byte[] StreamToByteArray(Stream inputStream)

    {

        if (!inputStream.CanRead)

        {

            throw new ArgumentException();

        }

        // This is optional

        if (inputStream.CanSeek)

        {

            inputStream.Seek(0, SeekOrigin.Begin);

        }

        byte[] output = new byte[inputStream.Length];

        int bytesRead = inputStream.Read(output, 0, output.Length);

        Debug.Assert(bytesRead == output.Length, "Bytes read from stream matches stream length");

        return output;

    }

private void DecryptPasswordprotectedPDF(string strPDFPath, string strPassword)

    {

        try

        {

            byte[] btPassword;

            btPassword = StrToByteArray(strPassword);

            Stream input = new FileStream(strPDFPath, FileMode.Open, FileAccess.Read, FileShare.Read);

            byte[] btSourceFile = StreamToByteArray(input);

            input.Close();

            PdfReader reader = new PdfReader(btSourceFile, btPassword);

            ////@+ decryption routine

            if (reader.IsOpenedWithFullPermissions)

            {

                PdfStamper pdfstmpr = new PdfStamper(reader, new FileStream(strPDFPath, FileMode.Create, FileAccess.Write, FileShare.None));

                pdfstmpr.Close();

            }

        }

        catch

        {

        }

    }

    public static byte[] StrToByteArray(string str)

    {

        System.Text.UTF8Encoding encoding = new System.Text.UTF8Encoding();

        return encoding.GetBytes(str);

    }