How to Merge Several PDF Docouments into One with C#/VB.NET

Sometimes, we may need to merge one document into one, or inset some pages of one PDF to another one.  For example, we download two PDF documents. One shows the first part of one story and the other shows the next part. In order to have one whole story document, we can merge them into one. In this post, I will introduce a method about how to merge PDF by using C#/VB.NET.

In my example, I prepare three documents. What I will do is to merge document 1 and document 2 into one and insert even pages of document 3 into the merged document.

I use a .NET PDF component, Spire.PDF for .NET in this method, so I add its dll file as reference in my project at the beginning. Then, we can start with coding.


  1. Load PDF documents. Because there are three documents, I create a list and put them in an array. The documents are put in doc[0], doc[1], doc[2] respectively.
  2. Merge doc[0] and doc[1]. Append page in doc[0], the page is the whole doc[1] document.
  3. Insert even page of doc[2] in doc[0]. Use a for loop to get even pages in doc[2] and insert these pages.
  4. Save the merged file and launch.



using System;
using Spire.Pdf;

namespace MergePDF
    class Merge
        static void Main(string[] args)
            //PDF Document List
            String[] files = new String[]
                @”D:\work\My Documents\A Thousand Suns.pdf”,
                @”D:\work\My Documents\easily cook.pdf”,
                @”D:\work\My Documents\Troubleshooting Guide Template.pdf”

            //Open PDF Documents   
            PdfDocument[] docs = new PdfDocument[files.Length];
            for (int i = 0; i < files.Length; i++)
                docs[i] = new PdfDocument(files[i]);

            //Append Document

            //Import Page
            for (int i = 0; i < docs[2].Pages.Count; i = i + 2)
                docs[0].InsertPage(docs[2], i);

            //Save and Launch
            foreach (PdfDocument doc in docs)


Imports System
Imports Spire.Pdf

Namespace MergePDF
       Friend Class Merge
              Shared Sub Main(ByVal args() As String)
                     ‘PDF Document List
                     Dim files() As String = { “D:\work\My Documents\A Thousand Suns.pdf”, “D:\work\My Documents\easily cook.pdf”, “D:\work\My Documents\Troubleshooting Guide Template.pdf” }

                     ‘Open PDF Documents   
                     Dim docs(files.Length – 1) As PdfDocument
                     For i As Integer = 0 To files.Length – 1
                           docs(i) = New PdfDocument(files(i))
                     Next i

                     ‘Append Document

                     ‘Import Page
                     For i As Integer = 0 To docs(2).Pages.Count – 1 Step 2
                           docs(0).InsertPage(docs(2), i)
                     Next i

                     ‘Save and Launch
                     For Each doc As PdfDocument In docs
                     Next doc
              End Sub
       End Class
End Namespace

Result Shown by Following:

Freely Download Spire.PDF for .NET


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