Based on https://ironpdf.com/how-to/java-merge-pdf-tutorial/

PDF stands for Portable Document Format, which is a digital representation of documents incorporating text and images. This format maintains consistent presentation and structure across varying platforms, devices, and software.

Java, known for its high-level, platform-independent capabilities, mirrors the universal nature of PDFs. This similarity facilitates seamless transitions across different computing environments. However, handling source PDF files and input streams in Java might pose complexities. IronPDF, a Java library, simplifies these tasks by providing robust tools for manipulating existing PDFs.

This tutorial will guide you through installing the IronPDF Java library and combining several PDF documents into one.

IronPDF serves as a toolkit for Java, enabling the creation, reading, and modification of single or multiple PDF documents. It empowers users to construct PDFs from scratch, incorporating rich content and style via HTML rendering, and also facilitates the insertion of metadata like titles and author details. Furthermore, it supports merging various PDFs into a single output file. This undertaking demands no auxiliary libraries, frameworks, or platform-specific integrations. IronPDF boasts Cross-Platform Support and is specifically engineered for Java 8+, Kotlin, and Scala across Windows, Linux, and various Cloud platforms.

Before initiating the merge process, ensure you have:

1. A Java-capable IDE (e.g., Netbeans, Eclipse, IntelliJ) — for this demonstration, IntelliJ will be used.
2. A Maven project set up in your IDE.

To start merging PDF files, the first step involves integrating the IronPDF Java library into your project. There are several methods to achieve this:

1. Insert the IronPDF dependency into the pom.xml of your Maven project and utilize either the command-line or an IDE to facilitate automatic library retrieval from the central repository.
2. Alternatively, procure the latest IronPDF version directly from the Maven repository here.
3. Another option is to download from the IronPDF official website using this link.

Add the following dependency snippet to your pom.xml:

<dependency>
    <groupId>com.ironsoftware</groupId>
    <artifactId>ironpdf</artifactId>
    <version>YOUR_VERSION_HERE</version>
</dependency>

Additionally, to merge PDFs, include Slf4j-simple in your project via this dependency or visit the Maven repository here.

<dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-simple</artifactId>
    <version>2.0.5</version>
</dependency>

The following import statements are necessary in your main.java file to take advantage of the IronPDF's functionalities:

import com.ironsoftware.ironpdf.PdfDocument;
import java.io.IOException;
import java.nio.file.Paths;

To merge PDF files, starting with PDF creation and culminating in a combined PDF file, use the following example:

String htmlA = "<p>PDF_A Content</p>