How to add Text to PDF?

package com.livrona.snippets.pdf;

import java.io.IOException;
import java.util.List;

import org.apache.pdfbox.exceptions.COSVisitorException;
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.pdfbox.pdmodel.common.PDRectangle;
import org.apache.pdfbox.pdmodel.edit.PDPageContentStream;
import org.apache.pdfbox.pdmodel.font.PDFont;
import org.apache.pdfbox.pdmodel.font.PDType1Font;

publicclass AddTextToPDF {
/**
	 * Constructor.
	 */
public AddTextToPDF() {
super();
	}

/**
	 * Add Text to PDF
	 * @param file
	 * @param message
	 * @param outfile
	 * @throws IOException
	 * @throws COSVisitorException
	 */
publicvoid doIt(String file, String message, String outfile)
throws IOException, COSVisitorException {
// the document
		PDDocument doc =null;
try {
// load the document
			doc = PDDocument.load(file);

// get all pages
			List allPages = doc.getDocumentCatalog().getAllPages();

// define the font size and type
			PDFont font = PDType1Font.HELVETICA_BOLD;
float fontSize =12.0f;

// loop through all pages
for (int i =0; i < allPages.size(); i++) {
				// get handle of the ith pag
				PDPage page = (PDPage) allPages.get(i);

				PDRectangle pageSize = page.findMediaBox();
float stringWidth = font.getStringWidth(message);

				// get page center
float centeredPosition = (pageSize.getWidth() - (stringWidth * fontSize) / 1000f) / 2f;

				// get the page steam
				PDPageContentStream contentStream =new PDPageContentStream(
						doc, page, true, true);
				// write the text with beginText , draw the message, endText
				contentStream.beginText();
				// set the font and size
				contentStream.setFont(font, fontSize);
				// set the text position x,y
				contentStream.moveTextPositionByAmount(centeredPosition, 30);
				contentStream.drawString(message); // draw it
				contentStream.endText();

				// close the stream for that page
				contentStream.close();
			}

// save the updated document to the new file
			doc.save(outfile);
		} finally {
if (doc !=null) {
				doc.close();
			}
		}
	}

/**
	 * This will create a hello world PDF document. see usage() for command line
	 * 
	 * @param args
	 *            Command line arguments.
	 */
publicstaticvoid main(String[] args) {
		AddTextToPDF app =new AddTextToPDF();
try {
if (args.length !=3) {
				app.usage();
			} else {
				app.doIt(args[0], args[1], args[2]);
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

/**
	 * This will print out a message telling how to use this example.
	 */
privatevoid usage() {
		System.err.println("usage: "+this.getClass().getName()
+"<input-file> <Message> <output-file>");
	}
}