AddAttachedFile

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using Bytescout.PDF;
namespace DemoProject
{
  class Program
  {
    static void Main(string[] args)
    {
      // Create main PDF Doc Engine
      PDFDocEngine engine = new PDFDocEngine("demo", "demo");
      // Add new document
      Document document = engine.AddDocument();
      // Append new page to the document
      Page page = document.AddPage(PageSizeType.A3, PageOrientationType.LandScape);
      document.AddAttachedFile("HelloWorld.pdf", "HelloWorld.pdf", "HelloWorld", false);
      // Save document
      document.Save("AddAttachedFile.pdf");
    }
  }
}