Graphics DrawImage does not work on some PDFs

private FileResult JoinPdfwithAnnotations(string imageData, MemoryStream stream, string contentType, string fileName)
{
   byte[] pdfBytes;
 
   //Returns the pdf document without annotations
   if (string.IsNullOrEmpty(imageData)) {
      pdfBytes = stream.ToArray();
      return File(pdfBytes, contentType, fileName);
   }
 
   List<string> base64AnnotationsList = imageData.Split(',').ToList();
   PdfLoadedDocument pdfDocument = new PdfLoadedDocument(stream);
   try {
      foreach (string base64Annotation in base64AnnotationsList) {
         PdfImage image;
         byte[] data = Convert.FromBase64String(base64Annotation);
         using (MemoryStream imageStream = new MemoryStream(data, 0, data.Length)) {
            image = PdfImage.FromStream(imageStream);
         }
         PdfLoadedPage pdfPage = (PdfLoadedPage) pdfDocument.Pages[base64AnnotationsList.IndexOf(base64Annotation)];
        
         if (pdfPage != null) {
            PdfGraphics gfx = pdfPage.Graphics;
            gfx.DrawImage(image, 0, 0);
         } else {
            LogManager.Instance.Error($"The image cannot be draw on pdf {fileName}");
         }
 
         pdfDocument.Save();
      }
      
      pdfBytes = stream.ToArray();
   } finally {
      pdfDocument.Close(true);
      stream.Close();
   }
 
   return File(pdfBytes, contentType, fileName);
}