Add Attachments to PDF in Java

import com.spire.pdf.annotations.*;
import com.spire.pdf.attachments.PdfAttachment;
import com.spire.pdf.graphics.*;

import java.awt.*;
import java.awt.geom.Dimension2D;
import java.awt.geom.Rectangle2D;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

public class AttachFiles {

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

        //create a PdfDocument object
        PdfDocument doc = new PdfDocument();

        //load a sample PDF file
        doc.loadFromFile("C:\\Users\\Administrator\\Desktop\\Sample.pdf");

        //add an attachment to pdf
        PdfAttachment attachment = new PdfAttachment("C:\\Users\\Administrator\\Desktop\\ReadMe.txt");
        doc.getAttachments().add(attachment);

        //draw a label on pdf
        String label = "Report.docx";
        PdfTrueTypeFont font = new PdfTrueTypeFont(new Font("Arial", Font.BOLD, 14));
        double x = 30;
        double y = doc.getPages().get(0).getActualSize().getHeight() - 100;
        doc.getPages().get(0).getCanvas().drawString(label, font, PdfBrushes.getOrange(), x, y);

        //add an attachment annotation to pdf
        String filePath = "C:\\Users\\Administrator\\Desktop\\Report.docx";
        byte[] data = toByteArray(filePath);
        Dimension2D size = font.measureString(label);
        Rectangle2D bound = new Rectangle2D.Float((float) (x + size.getWidth() + 2), (float) y, 10, 15);
        PdfAttachmentAnnotation annotation = new PdfAttachmentAnnotation(bound, filePath, data);
        annotation.setColor(new PdfRGBColor(new Color(0, 128, 128)));
        annotation.setFlags(PdfAnnotationFlags.Default);
        annotation.setIcon(PdfAttachmentIcon.Graph);
        annotation.setText("Click to open Report.docx");
        doc.getPages().get(0).getAnnotationsWidget().add(annotation);

        //save to file
        doc.saveToFile("Attachments.pdf");
    }

    //read file to byte array
    public static byte[] toByteArray(String filePath) throws IOException {

        File file = new File(filePath);
        long fileSize = file.length();
        if (fileSize > Integer.MAX_VALUE) {
            System.out.println("file too big...");
            return null;
        }
        FileInputStream fi = new FileInputStream(file);
        byte[] buffer = new byte[(int) fileSize];
        int offset = 0;
        int numRead = 0;
        while (offset < buffer.length
                && (numRead = fi.read(buffer, offset, buffer.length - offset)) >= 0) {
            offset += numRead;
        }

        if (offset != buffer.length) {
            throw new IOException("Could not completely read file "
                    + file.getName());
        }
        fi.close();
        return buffer;
    }
}