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How to merge PDF files in C#, VB.NET

Platform: WinForms |
Control: PDF

Syncfusion Essential PDF is a .NET PDF library that allows you to combine or merge different PDF files into one file quickly and accurately. Merge PDF functionalities can be used in any .NET application, whether it is Windows Forms, WPF, ASP.NET (web forms, MVC, Core) or even UWP, Xamarin.Forms, Xamarin.Android, and Xamarin.iOS. It will help you combine, import, and append PDFs with just a few lines of code using C# or VB.NET.

Steps to merge multiple PDF files programmatically:

  1. Create a new C# console application project. Create a console application in Visual Studio
  2. Install the Syncfusion.Pdf.WinForms NuGet package as reference to your .NET Framework applications from NuGet.org. NuGet package reference screenshot
  3. Include the following namespaces in the Program.cs file.


using Syncfusion.Pdf;
using System.IO;



Imports Syncfusion.Pdf
Imports System.IO


  1. Use the Merge() method with source parameter that is an string array of PDF files to get the merged final PDF document in finalDoc.
    // Merges PDFDocument
    PdfDocumentBase.Merge(finalDoc, source);


  1. Use the following C# and VB.NET code snippet to merge multiple PDF documents from disk.


//Creates a PDF document
PdfDocument finalDoc = new PdfDocument();
//Creates a string array of source files to be merged
string[] source = { "file1.pdf", "file2.pdf" };
//Merge PDF documents
PdfDocumentBase.Merge(finalDoc, source);
//Save the document
//Close the document



'Creates a PDF document
Dim finalDoc As New PdfDocument()
'Creates a string array of source files to be merged
Dim source As String() = {"file1.pdf", "file2.pdf"}
'Merge PDF documents
PdfDocumentBase.Merge(finalDoc, source)
'Save the document
'Close the document


A complete working sample can be downloaded from MergePDFSample.zip.

The inputs of the PDF document are as follows.

Input 1 Input file to be merged

Input 2 Input file to be merged

By executing the program, you will get the merged PDF document as follows. Ouput of Merged PDF file

Take a moment to peruse the documentation to merge the multiple PDF documents with string array and importing pages from multiple documents with Essential PDF. Also,  brief details about split, delete and rotate PDF pages are available with code examples.

Refer here to explore the rich set of Syncfusion Essential PDF features.

An online sample link to merge PDF documents.


Starting with v16.2.0.x, if you reference Syncfusion assemblies from trial setup or from the NuGet feed, include a license key in your projects. Refer to link to learn about generating and registering Syncfusion license key in your application to use the components without trail message.


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Jordan Capa
Apr 23, 2019

very helpful article! i recommend zetpdf.com for merging or converting pdf files in vb.net. it is very easy to use and convenient.


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