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How to merge all PDF files in a folder in C# and VB.NET?

5 mins read

The Syncfusion Essential PDF is a feature-rich and high performance .NET PDF library used to create, read, and edit PDF documents programmatically without Adobe dependencies. This library also offers functionality to merge, split, stamp, forms, compress, and secure PDF files.

This sample explains how to merge all PDF files in a folder into single PDF using Syncfusion .NET PDF library.

Steps to merge all PDF files in a folder programmatically in C#:

  1. Create a new console application project. Create a console application in Visual Studio in .NET PDF
  2. Install the Syncfusion.Pdf.WinForms NuGet package as a reference to your .NET Framework application from Refer NuGet package to the project in .NET PDF
  3. You can merge two PDF documents by using the Merge method of PdfDocumentBase class.


//Merge PDF file
PdfDocumentBase.Merge(document, loadedDocument);



'Merge PDF file
PdfDocumentBase.Merge(document, loadedDocument)


  1. Include the following namespaces in Program.cs file.


using Syncfusion.Pdf;
using Syncfusion.Pdf.Parsing;
using System.IO;



Imports System.IO
Imports Syncfusion.Pdf
Imports Syncfusion.Pdf.Parsing


  1. Include the following code snippet in main method of Program.cs file to merge all PDF files in a folder into single PDF document.


//Get the folder path into DirectoryInfo
DirectoryInfo directoryInfo = new DirectoryInfo("../../Data/");
//Get the PDF files in folder path into FileInfo
FileInfo[] files = directoryInfo.GetFiles("*.pdf");
//Create a new PDF document 
PdfDocument document = new PdfDocument();
//Set enable memory optimization as true 
document.EnableMemoryOptimization = true;
foreach (FileInfo file in files)
    //Load the PDF document 
    FileStream fileStream = new FileStream(file.FullName, FileMode.Open);
    PdfLoadedDocument loadedDocument = new PdfLoadedDocument(fileStream);
    //Merge PDF file
    PdfDocumentBase.Merge(document, loadedDocument);
    //Close the existing PDF document 
//Save the PDF document
//Close the instance of PdfDocument



'Get the folder path into DirectoryInfo
Dim directoryInfo As DirectoryInfo = New DirectoryInfo("../../Data/")
'Get the PDF files in folder path into FileInfo
Dim files() As FileInfo = directoryInfo.GetFiles("*.pdf")
'Create a new PDF document 
Dim document As PdfDocument = New PdfDocument
'Set enable memory optimization as true 
document.EnableMemoryOptimization = True
For Each file As FileInfo In files
    'Load the PDF document 
    Dim fileStream As FileStream = New FileStream(file.FullName, FileMode.Open)
    Dim loadedDocument As PdfLoadedDocument = New PdfLoadedDocument(fileStream)
    'Merge PDF file
    PdfDocumentBase.Merge(document, loadedDocument)
    'Close the existing PDF document 
'Save the PDF document
'Close the instance of PdfDocument


A complete work sample to merge all PDF documents in a folder into single PDF document can be downloaded from

Place the files of different file formats in the data folder of project and execute the program to see the merged PDF document created by merging all the PDF files in the folder.

Take a moment to peruse the documentation, where you will find other options like RTF to PDF conversion, XPS to PDF conversion, PDF to image conversion, HTML to MHTML, HTML to SVG, partial webpage to SVG, and more.

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

An online sample link to convert word document to PDF, RTF to PDF, XPS to PDF, TIFF to PDF, PDF to Image, and excel document to PDF.


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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