code: public String getPDFPageAnnotationName() {
  
      Properties mappings = input.getMappings();
  
      if (mappings != null) {
        return mappings.getProperty(MAPPING_PAGE_KEY,
                DEFAULT_PAGE_NUMBER_ANNOTATION_NAME);
      }
  
      return DEFAULT_PAGE_NUMBER_ANNOTATION_NAME;
    }
docs: Gets the pdf page annotation name. It takes into acount the mappings
  defined in {@link VisualizerInput#mappings}.