Merge PDF documents - Apache PDFBox example

import java.io.File;
import java.io.IOException;
import java.util.Random;

import org.apache.pdfbox.io.MemoryUsageSetting;
import org.apache.pdfbox.multipdf.PDFMergerUtility;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.PDPageContentStream;
import org.apache.pdfbox.pdmodel.common.PDRectangle;
import org.apache.pdfbox.pdmodel.font.PDType1Font;


public class MergePDFs {

	public static void main(String[] args) {

		try {

			//Creating PDF document object 
			String myPDF1 = "docs/my_doc1.pdf";
			PDDocument document1 = new PDDocument();

			//Add Random number of Pages in your document
			Random generator = new Random();
			int myCount = generator.nextInt(10) + 1;
			for(int i=0; i < myCount; i++){
				PDPage page = new PDPage(PDRectangle.LETTER);
				document1.addPage(page);
				addText(document1,page,i+1);
			}


			document1.save(myPDF1);
			document1.close();

			//Creating PDF document object 
			String myPDF2 = "docs/my_doc2.pdf";
			PDDocument document2 = new PDDocument();

			//Add Random number of Pages in your document
			int newCount = generator.nextInt(10) + myCount + 1;
			for(int i=myCount; i < newCount; i++){
				PDPage page = new PDPage(PDRectangle.LETTER);
				document2.addPage(page);
				addText(document2,page,i+1);
			}

			document2.save(myPDF2);
			document2.close();

			//Now let's merge the 2 documents
			//instantiate the merge utility class
			File file1 = new File(myPDF1);
			File file2 = new File(myPDF2);
			PDFMergerUtility pdfMerger = new PDFMergerUtility(); 
			pdfMerger.setDestinationFileName("docs/merged.pdf");
			pdfMerger.addSource(file1);
			pdfMerger.addSource(file2);
			pdfMerger.mergeDocuments(MemoryUsageSetting.setupMainMemoryOnly());
			file1.delete();
			file2.delete();


		} catch (IOException e) {
			e.printStackTrace();
		}

	}

	private static void addText(PDDocument document, PDPage page, int pageNo) {

		try {

			PDPageContentStream contentStream = new PDPageContentStream(document, page, PDPageContentStream.AppendMode.APPEND, true);
			contentStream.beginText(); 
			contentStream.setFont(PDType1Font.HELVETICA, 12);
			contentStream.newLineAtOffset(25,750);
			contentStream.showText("This is Page No: " + pageNo);      
			contentStream.endText();
			contentStream.close();

		} catch (IOException e) {
			e.printStackTrace();
		}

	}


}