如何将 bmp 另存为 pdf

我正在保存图像，但我需要将此图像转换为pdf并保存。我该怎么做？

这是我使用的代码：

private void button3_Click(object sender, EventArgs e)
    {
        SaveFileDialog saveFileDialog1 = new SaveFileDialog();
        saveFileDialog1.FileName = "image.bmp";
        if (saveFileDialog1.ShowDialog() == DialogResult.OK)
        {
            Bitmap bitmap = new Bitmap(this.Width, this.Height);
            this.DrawToBitmap(bitmap, this.ClientRectangle);
            using (var Stream = saveFileDialog1.OpenFile())
            {
                bitmap.Save(Stream, ImageFormat.Bmp);
            }
        }
}

void DrawImage(XGraphics gfx, int number)
{
  BeginBox(gfx, number, "DrawImage (original)");
  XImage image = XImage.FromFile(jpegSamplePath);
  // Left position in point
  double x = (250 - image.PixelWidth * 72 / image.HorizontalResolution) / 2;
  gfx.DrawImage(image, x, 0);
  EndBox(gfx);
}