How can replace words in pdf file in java?

I tried code like this, but it's not replacing words. Is it correct way to replace words in pdf file?

@SpringBootApplication
public class DocReadWriteApplication {

    public static final String SRC = "../Downloads/Debt LOI.pdf";
    public static final String DEST = "../Downloads/hello.pdf";

    public static void main(String[] args) throws IOException, DocumentException {
        File file = new File(DEST);
        file.getParentFile().mkdirs();
        manipulatePdf(SRC, DEST);
    }

    public static void manipulatePdf(String src, String dest) throws IOException, DocumentException {
        PdfReader reader = new PdfReader(src);
        PdfDictionary dict = reader.getPageN(1);
        PdfObject object = dict.getDirectObject(PdfName.CONTENTS);
        PdfArray refs = null;
        if (dict.get(PdfName.CONTENTS).isArray()) {
            refs = dict.getAsArray(PdfName.CONTENTS);
        } else if (dict.get(PdfName.CONTENTS).isIndirect()) {
            refs = new PdfArray(dict.get(PdfName.CONTENTS));
        }
        for (int i = 0; i < refs.getArrayList().size(); i++) {
            PRStream stream = (PRStream) refs.getDirectObject(i);
            byte[] data = PdfReader.getStreamBytes(stream);
            stream.setData(new String(data).replace("transaction", "Data").getBytes());
        }
        PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(dest));
        stamper.close();
        reader.close();
    }
}

Anybody have done like this?