PDFBox - Merging Multiple PDF Documents

In the previous chapter, we have seen how to split a given PDF document into multiple documents. Let us now learn how to merge multiple PDF documents as a single document.

Merging Multiple PDF Documents

You can merge multiple PDF documents into a single PDF document using the class named PDFMergerUtility class, this class provides methods to merge two or more PDF documents in to a single PDF document.
Following are the steps to merge multiple PDF documents.

Step 1: Loading an Existing PDF Document

Load an existing PDF document using the static method load() of the PDDocument class. This method accepts a file object as a parameter, since this is a static method you can invoke it using class name as shown below.

File file = new File("path of the document") 
PDDocument document = PDDocument.load(file);

Step 2: Instantiating the PDFMergerUtility class

instantiate the merge utility class as shown below.

PDFMergerUtility PDFmerger = new PDFMergerUtility(); 

Step 3: Setting the destination file

Set the destination files using the setDestinationFileName() method as shown below.

PDFmerger.setDestinationFileName("C:/PdfBox_Examples/data1/merged.pdf");

Step 4: Setting the source files

Set the source files using the addSource() method as shown below.

PDFmerger.addSource(file1);

Step 5: Merging the documents

Mergr the documents using the mergeDocuments() method of the PDFmerger class as shown below.

PDFmerger.addSource(file1);

Step 6: Closing the Document

Finally close the document using close() method of PDDocument class as shown below.

document.close();

Example

Suppose, we have two PDF documents — sample1.pdf and sample2.pdf, in the path C:\PdfBox_Examples\ as shown below.
This example demonstrates how to merge the above PDF documents. Here, we will merge the PDF documents named sample1.pdf and sample2.pdf in to a single PDF document merged.pdf. Save this code in a file with name MergePDFs.java.

import org.apache.pdfbox.multipdf.PDFMergerUtility;
import org.apache.pdfbox.pdmodel.PDDocument;
  
import java.io.File; 
import java.io.IOException;

public class MergePDFs {
   public static void main(String[] args) throws IOException {

      //Loading an existing PDF document
      File file1 = new File("C:/PdfBox_Examples/sample1.pdf");
      PDDocument doc1 = PDDocument.load(file1);
       
      File file2 = new File("C:/PdfBox_Examples/sample2.pdf");
      PDDocument doc2 = PDDocument.load(file2);
         
      //Instantiating PDFMergerUtility class
      PDFMergerUtility PDFmerger = new PDFMergerUtility();

      //Setting the destination file
      PDFmerger.setDestinationFileName("C:/PdfBox_Examples/merged.pdf");

      //adding the source files
      PDFmerger.addSource(file1);
      PDFmerger.addSource(file2);

      //Merging the two documents
      PDFmerger.mergeDocuments();

      System.out.println("Documents merged");
      //Closing the documents
      doc1.close();
      doc2.close();
   }

}

Compile and execute the saved Java file from the command prompt using the following commands.

javac MergePDFs.java 
java MergePDFs 

Upon execution, the above program encrypts the given PDF document displaying the following message.

Documents merged

If you verify the given path, you can observe that a PDF document with name merged.pdf is created and this contains the pages of both the source documents as shown below.