iText Knowledge Base

Merging PDF files has become a common need for many businesses and individuals. It allows you to combine multiple PDF documents into a single, unified file, providing convenience and organization. Whether you want to merge invoices, reports, or other types of documents, this process simplifies document management and enhances overall productivity.

In this blog post, we will explore how to merge PDF files using the open-source .NET API, iTextPdf. We will delve into the merging functionality offered by iTextPdf for .NET, providing a step-by-step guide and an accompanying C# code sample. By the end, you’ll have the knowledge and tools to effortlessly merge multiple PDFs into a single, cohesive document.

Benefits of Merging PDF Files

Before we dive into the technical aspects, let’s highlight the numerous benefits of merging PDF files. By merging, you can:

  1. Streamline document management: Combining multiple PDFs eliminates the hassle of handling separate files, making it easier to organize, store, and share information.
  2. Enhance readability: Consolidating related content into a single PDF ensures smooth navigation and a seamless reading experience for your audience.
  3. Improve collaboration: When collaborating on projects or sharing documents with colleagues, merging PDFs avoids confusion and promotes efficient teamwork.

Introduction to iTextPdf for .NET

iTextPdf is a powerful open-source library for working with PDF files in the .NET environment. It provides extensive functionality for creating, manipulating, and merging PDF documents programmatically, making it an excellent choice for merging multiple PDF files seamlessly.

How to Merge PDF Files using iTextPdf in C#?

Multiple PDF files can be merged into a single PDF using the following steps.

  1. Install iTextPdf in your .NET project using NuGet package manager.
  2. Import the necessary namespaces and create a new PDF document object.
  3. Iterate through the list of PDF files to be merged and open each file using iTextPdf’s PdfReader.
  4. Create a new PdfCopy object and add the pages from each PDF file to the merged document.
  5. Save the merged document to the desired location.

The following C# code demonstrates how to merge multiple PDF files into a single large PDF file.

string[] fileNames = {"splitDocument_1.pdf", "splitDocument_2.pdf", "splitDocument_3.pdf", "splitDocument_4.pdf", "splitDocument_5.pdf", 
splitDocument_6.pdf","splitDocument_7.pdf","splitDocument_8.pdf","splitDocument_9.pdf","splitDocument_10.pdf" };
string mergedFileName = "Merged.pdf";
using (var mergedDocument = new PdfDocument(new PdfWriter(mergedFileName)))
    foreach (var fileName in fileNames)
        using (var pdfDocument = new PdfDocument(new PdfReader(fileName)))
            pdfDocument.CopyPagesTo(1, pdfDocument.GetNumberOfPages(), mergedDocument);

To ensure a comprehensive understanding of the code sample, let’s explore the essential API calls and methods used:

  1. PdfReader: This class enables you to read a PDF document and extract its content, such as pages and metadata.
  2. PdfCopy: The PdfCopy class allows you to create a new PDF document and add pages from multiple source documents to the merged output.
  3. AddPage(): This method is used to add a page from a source PDF file to the merged document using the PdfCopy object.
  4. Save(): After all the necessary pages are added, the Save() method is called to save the merged PDF document to a specified file location.


Merging PDF files using iTextPdf for .NET offers a seamless and efficient solution for managing and organizing multiple documents. By consolidating related content into a single PDF, you can enhance readability, streamline collaboration, and improve overall productivity.

In this blog post, we introduced the concept of merging PDF files and highlighted the benefits it brings. We also provided an overview of iTextPdf for .NET and a detailed code sample for merging multiple PDFs using this powerful open-source library. With the step-by-step guide and explanation of essential API calls and methods, you now have the necessary knowledge to merge PDF files effortlessly. Stay tuned for more examples in this blog.