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

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.
2. Install the Syncfusion.Pdf.WinForms NuGet package as reference to your .NET Framework applications from NuGet.org.
3. Include the following namespaces in the Program.cs file.

C#

using Syncfusion.Pdf;
using System.IO;

VB.NET

Imports Syncfusion.Pdf
Imports System.IO

4. 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);
   

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

C#

//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
finalDoc.Save("Sample.pdf");
 
//Close the document
finalDoc.Close(true); 

VB.NET

'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
finalDoc.Save("Sample.pdf")
 
'Close the document
finalDoc.Close(True)

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

The inputs of the PDF document are as follows.

Input 1

Input 2

By executing the program, you will get the merged PDF document as follows.

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.

Conclusion

I hope you enjoyed learning about a C# example to merge PDF files using Syncfusion .NET PDF library.

You can refer to our WinForms PDF feature tour page to know about its other groundbreaking feature representations and documentation, and how to quickly get started for configuration specifications. You can also explore our 
WinForms PDF example to understand how to create and manipulate data.

For current customers, you can check out our components from the License and Downloads page. If you are new to Syncfusion, you can try our 30-day free trial to check out our other controls.

If you have any queries or require clarifications, please let us know in the comments section below. You can also contact us through our support forums, Direct-Trac, or feedback portal. We are always happy to assist you!