Is there any good way to combine two PDF files?

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Merge PDFs in reverse order:

Cross merge PDFs

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The following codes will show you how to combine PDF files in programming languages like ASP.NET, C#, and VB.NET.

C# code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Call_PDFToolBoxCom
{
    class Program
    {
     static void Main(string[] args)
     {
         string strExePath = System.AppDomain.CurrentDomain.SetupInformation.ApplicationBase;
         PDFToolBoxCom.PDFToolBoxCom p = new PDFToolBoxCom.PDFToolBoxCom();
         string strReturn = p.RunCMD("A=" + strExePath + @"\even.pdf"+" B=" + strExePath + @"\odd.pdf -crossmerge A B -outfile " + strExePath + @"\collated.pdf");
         Console.WriteLine(strReturn);
         Console.WriteLine("Please enter any key to continue...");
         Console.ReadKey();
      }
   }
}

VB.NET code:   Cross merge PDFs
Module Module1
    Sub Main()
        Dim p As PDFToolBoxCom.PDFToolBoxCom
        Dim strRet As String
        Dim strParam As String
        Dim strPath As String
        strPath = AppDomain.CurrentDomain.SetupInformation.ApplicationBase
strParam = strPath + "pdftoolbox.exe A=" + strPath + "even.pdf" + " B=" + strPath + "odd.pdf -crossmerge A B -outfile " + strPath + "collated.pdf"
        Console.WriteLine(strParam)
        p = New PDFToolBoxCom.PDFToolBoxCom()
        strRet = p.RunCMD(strParam)
        Console.WriteLine(strRet)
        Console.WriteLine("Please enter any key to continue...")
        Console.ReadKey()
    End Sub
End Module

VB.NET code:   Merge PDFs in reverse order
Module Module1
    Sub Main()
        Dim p As PDFToolBoxCom.PDFToolBoxCom
        Dim strRet As String
        Dim strParam As String
        Dim strPath As String
        strPath = AppDomain.CurrentDomain.SetupInformation.ApplicationBase
strParam = strPath + "pdftoolbox.exe A=" + strPath + "even.pdf" + " B=" + strPath + "odd.pdf -crossmerge A Bend-1 -outfile " + strPath + "collated.pdf"
        Console.WriteLine(strParam)
        p = New PDFToolBoxCom.PDFToolBoxCom()
        strRet = p.RunCMD(strParam)
        Console.WriteLine(strRet)
        Console.WriteLine("Please enter any key to continue...")
        Console.ReadKey()
    End Sub
End Module

ASP_NET code: Cross merge PDFs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace ASP_NET_Call_PDFToolBoxCom
{
     public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {}
        protected void Button1_Click(object sender, EventArgs e)
        {
            Console.WriteLine("UserName: {0}", Environment.UserName);
            PDFToolBoxCom.PDFToolBoxCom p = new PDFToolBoxCom.PDFToolBoxCom();
            string strPath = @"E:\bin\pdftoolbox.exe";
            strPath += @" A=even.pdf B=odd.pdf -crossmerge A B -outfile collated.pdf";
            string strRet = p.RunCMD(strPath);
            Response.Write(strRet);
        }
    }
}

ASP_NET code:   Merge PDFs in reverse order:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace ASP_NET_Call_PDFToolBoxCom
{
    public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {}
        protected void Button1_Click(object sender, EventArgs e)
       {
           Console.WriteLine("UserName: {0}", Environment.UserName);
           PDFToolBoxCom.PDFToolBoxCom p = new PDFToolBoxCom.PDFToolBoxCom();
           string strPath = @"E:\bin\pdftoolbox.exe";
           strPath += @" A=even.pdf B=odd.pdf -crossmerge A Bend-1 -outfile collated.pdf";
           string strRet = p.RunCMD(strPath);
           Response.Write(strRet); 
        }
    }
}