I’m using PDFBox version 3.0.2 (also tried on oldest version) to convert a file PDF containing e-signature to image JPG/PNG but missing a content

Here is my PDF file (screenshot)
enter image description here

And converted image file
enter image description here

try (PDDocument document = Loader.loadPDF(new File("test-signed.pdf"))) {
    PDFRenderer pdfRenderer = new PDFRenderer(document);
            
    BufferedImage bufferedImage = pdfRenderer.renderImage(0, 300 / 72f, ImageType.RGB, RenderDestination.PRINT);

    File file = new File("output.png");
    ImageIO.write(bufferedImage, "png", file);
}

I need render all contents in pdf to image

Why some e-signature can render but others cannot render? Anyone can help?