docs: def _validate_pdf_file(self):
          """Validate that the pdf_path configuration is set and the referenced
          file exists.
  
          Exits the program with status 1 if validation fails.
          """
          if self['pdf_path'] is None:
              self._logger.error('--pdf argument must be set')
              sys.exit(1)
          if not os.path.exists(self['pdf_path']):
              self._logger.error('Cannot find PDF ' + self['pdf_path'])
              sys.exit(1)