In file https://github.com/mozilla/pdf.js/files/5249872/product1.pdf, the fifth text widget has a default appearance using font F1 and this one is neither in DR nor in AcroForm but in AP::N::Resources.
case "Ink":
        return new InkAnnotation(parameters);
      case "Highlight":
        return new HighlightAnnotation(parameters);
      case "Underline":
        return new UnderlineAnnotation(parameters);
      case "Squiggly":
        return new SquigglyAnnotation(parameters);
      case "StrikeOut":
        return new StrikeOutAnnotation(parameters);
      case "Stamp":
        return new StampAnnotation(parameters);
      case "FileAttachment":
        return new FileAttachmentAnnotation(parameters);
      default:
        if (!subtype) {
          warn("Annotation is missing the required /Subtype.");
        } else {
          warn(
            'Unimplemented annotation type "' +
              subtype +
              '", ' +
              "falling back to base annotation."
          );
        }
        return new Annotation(parameters);
    }
  }
}
function getQuadPoints(dict, rect) {