How to Merge Two PDF Files Using Java

This article will demonstrate how to merge multiple PDF documents using IronPDF for Java. We will go through the process of setting up the environment, importing the library, reading the input files and merging them into a single document.

IronPDF for Java

IronPDF for Java is a powerful library that allows developers to create new PDF documents from scratch and convert various file formats to PDF documents. It also provides the ability to merge multiple PDF files into a single document.

IronPDF for Java is easy to use and has a simple and intuitive API that makes it easy for developers to create PDF files. It also supports methods to rendering charts in PDFs, work with PDF forms and even handle digital signatures programmatically.

Prerequisites

Before implementing, there are a few prerequisites that must be met to carry out the PDF creation process.

1. Java should be installed on your system and its path should be set in the environment variables. If you haven't installed Java yet, please refer to this installation guideline from Java website for instructions.
2. A Java IDE such as Eclipse or IntelliJ should be installed. You can download Eclipse from this download link and IntelliJ from this download link.
3. The IronPDF library for Java should be downloaded and added as a dependency in your project. You can visit the IronPDF website for instructions on how to do this.
4. Maven should be installed and integrated with your IDE before starting with PDF conversion. For a tutorial on installing Maven and integrating it into your environment, please visit this tutorial from JetBrains.

IronPDF for Java Installation

If all requirements are met, the installation of IronPDF for Java is quite simple and straightforward, even for Java novices.

For this article, JetBrain's IntelliJ IDEA will be used to install and run samples.

First, open JetBrains IntelliJ IDEA and create a new Maven project.

New Maven Project in IntelliJ

A new window will appear. Enter the name of the project and click on finish.

Name the Maven Project and click Finish

After you click Finish, a new project will open to a pom.xml to add Maven dependencies of IronPDF for Java.

The pom.xml file

Add the following dependencies in the pom.xml file or you can download the JAR file from the following down link from Maven repository.

<dependency>
   <groupId>com.ironsoftware</groupId>
   <artifactId>com.ironsoftware</artifactId>
   <version>2024.9.1</version>
</dependency>

Once you placed the dependencies in the pom.xml file, a small icon will appear in the right top corner of the file.

Click the floating icon to install the Maven dependencies automatically

Click on this icon to install the Maven dependencies of IronPDF for Java. This will only take a few minutes depending on your internet connection.

Merge Multiple PDF Documents

IronPDF allows you to merge multiple PDF documents into a single PDF document using a Java program. IronPDF provides several ways to merge PDF documents:

1. Create two new PDF documents and merge them to create one PDF.
2. Open input PDF files into a merged PDF.
3. Merge more than two PDF documents.

Creating Two New PDF Documents and Merge Them Together

import com.ironsoftware.ironpdf.PdfDocument;

import java.io.IOException;
import java.nio.file.Paths;

public class main {
    public static void main(String[] args) throws IOException {
        String htmlA = "<p> [PDF_1] </p>"
                + "<p> Hi this is the first PDF </p>";
        String htmlB = "<p> [PDF_2] </p>"
                + "<p> This is the 2nd PDF </p>";

        PdfDocument pdfA = PdfDocument.renderHtmlAsPdf(htmlA);
        PdfDocument pdfB = PdfDocument.renderHtmlAsPdf(htmlB);
        PdfDocument merged = PdfDocument.merge(pdfA, pdfB);

        merged.saveAs(Paths.get("assets/merged.pdf"));
    }
}

import com.ironsoftware.ironpdf.PdfDocument;

import java.io.IOException;
import java.nio.file.Paths;

public class main {
    public static void main(String[] args) throws IOException {
        String htmlA = "<p> [PDF_1] </p>"
                + "<p> Hi this is the first PDF </p>";
        String htmlB = "<p> [PDF_2] </p>"
                + "<p> This is the 2nd PDF </p>";

        PdfDocument pdfA = PdfDocument.renderHtmlAsPdf(htmlA);
        PdfDocument pdfB = PdfDocument.renderHtmlAsPdf(htmlB);
        PdfDocument merged = PdfDocument.merge(pdfA, pdfB);

        merged.saveAs(Paths.get("assets/merged.pdf"));
    }
}

New PDF File Merger

Combine Existing Files into One PDF

IronPDF allows you to merge existing PDF files into one common PDF file. Just specify the list of PDF input files. IronPDF will merge all PDF files into a single PDF document and save it to the destination file. The output will contain the result of the successfully merged PDF files.

import com.ironsoftware.ironpdf.PdfDocument;

import java.io.IOException;
import java.nio.file.Paths;

public class main {
    public static void main(String[] args) throws IOException {
        PdfDocument pdfA = PdfDocument.fromFile(Paths.get("assets/1.pdf"));
        PdfDocument pdfB = PdfDocument.fromFile(Paths.get("assets/2.pdf"));
        PdfDocument merged = PdfDocument.merge(pdfA, pdfB);

        merged.saveAs(Paths.get("assets/merged.pdf"));
    }
}

import com.ironsoftware.ironpdf.PdfDocument;

import java.io.IOException;
import java.nio.file.Paths;

public class main {
    public static void main(String[] args) throws IOException {
        PdfDocument pdfA = PdfDocument.fromFile(Paths.get("assets/1.pdf"));
        PdfDocument pdfB = PdfDocument.fromFile(Paths.get("assets/2.pdf"));
        PdfDocument merged = PdfDocument.merge(pdfA, pdfB);

        merged.saveAs(Paths.get("assets/merged.pdf"));
    }
}

Existing PDF Merger Output

Merging More Than Two PDF Documents

You can easily merge more than two PDF files using IronPDF for Java.

import com.ironsoftware.ironpdf.PdfDocument;

import java.io.IOException;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;

public class main {
    public static void main(String[] args) throws IOException {
        List<PdfDocument> pdfList = new ArrayList<>();
        pdfList.add(PdfDocument.fromFile(Paths.get("assets/1.pdf")));
        pdfList.add(PdfDocument.fromFile(Paths.get("assets/2.pdf")));
        pdfList.add(PdfDocument.fromFile(Paths.get("assets/3.pdf")));
        PdfDocument merged = PdfDocument.merge(pdfList);
        merged.saveAs(Paths.get("assets/merged.pdf"));
    }
}

import com.ironsoftware.ironpdf.PdfDocument;

import java.io.IOException;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;

public class main {
    public static void main(String[] args) throws IOException {
        List<PdfDocument> pdfList = new ArrayList<>();
        pdfList.add(PdfDocument.fromFile(Paths.get("assets/1.pdf")));
        pdfList.add(PdfDocument.fromFile(Paths.get("assets/2.pdf")));
        pdfList.add(PdfDocument.fromFile(Paths.get("assets/3.pdf")));
        PdfDocument merged = PdfDocument.merge(pdfList);
        merged.saveAs(Paths.get("assets/merged.pdf"));
    }
}

Conclusion

This article covers how to merge multiple PDF files using Java and the IronPDF library. By following the steps outlined in this article, you will be able to set up the environment, import the library, read the input files, and merge them into a single document.

For more information about merging two or more PDF files in Java and for similar tutorials on how to create and format PDFs using Java, read the Documentation pages.

IronPDF for Java is free for development purposes but requires a license for commercial use.