How To Read A Pdf File Using C# And Encrypt This File Using Aes.Below Is The Code, But I Get Only Blank Pdf File While Decrypting.Why?

string text = string.Empty;
        using (StreamReader streamReader = new StreamReader(@"D:\\Website examples\myproject\Final\RandomQuestionBank.pdf", Encoding.UTF8))
        {
            text = streamReader.ReadToEnd();
        }
      
       txt_encrypt.Text = this.Encrypt(text);
        var path = Server.MapPath("~/Final");
        var directinfo = new DirectoryInfo(path);
        if (directinfo.Exists)
        {
            var newfolder = directinfo.CreateSubdirectory("Encrypt Qbank");
            string encryptpath = Server.MapPath("~/" + newfolder + "\\" + "encrypt file");
            File.WriteAllText(encryptpath, txt_encrypt.Text);
            File.SetAttributes(encryptpath, FileAttributes.ReadOnly);

        }



    }
    private string Encrypt(string clearText)
    {
        string EncryptionKey = label_key.Text;
        byte[] clearBytes = Encoding.Unicode.GetBytes(clearText);
        using (Aes encryptor = Aes.Create())
        {
            Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(EncryptionKey, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });
            encryptor.Key = pdb.GetBytes(32);
            encryptor.IV = pdb.GetBytes(16);
            using (MemoryStream ms = new MemoryStream())
            {
                using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateEncryptor(), CryptoStreamMode.Write))
                {
                    cs.Write(clearBytes, 0, clearBytes.Length);
                    cs.Close();
                }
                clearText = Convert.ToBase64String(ms.ToArray());
            }
            txt_encrypt.Text = clearText;

        }
        return clearText;
    }