iText 7:如何将“第x页，共y页”放在右下角

import com.itextpdf.kernel.pdf.PdfDocument;
import com.itextpdf.kernel.pdf.PdfPage;
import com.itextpdf.kernel.pdf.PdfWriter;
import com.itextpdf.kernel.pdf.canvas.PdfCanvas;
import com.itextpdf.kernel.font.PdfFontFactory;
import com.itextpdf.kernel.geom.Rectangle;
import com.itextpdf.layout.Document;
import com.itextpdf.layout.element.Paragraph;

public class PdfPageNumberingExample {
    public static void main(String[] args) {
        String outputFile = "output.pdf";
        int totalPages = 10; // 总页数
        int currentPage = 1; // 当前页数

        try {
            PdfWriter writer = new PdfWriter(outputFile);
            PdfDocument pdfDoc = new PdfDocument(writer);
            Document document = new Document(pdfDoc);

            while (currentPage <= totalPages) {
                PdfPage page = pdfDoc.addNewPage();
                Rectangle pageSize = page.getPageSize();
                PdfCanvas canvas = new PdfCanvas(page);

                // 设置字体和字号
                canvas.setFontAndSize(PdfFontFactory.createFont(), 12);

                // 绘制文本
                canvas.showTextAligned(new Paragraph("第" + currentPage + "页，共" + totalPages + "页").setFont(PdfFontFactory.createFont()), 
                    pageSize.getRight() - 50, pageSize.getBottom() + 20, 0);

                currentPage++;
            }

            document.close();
            System.out.println("PDF生成成功！");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}