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.
/**
   * Create an `Annotation` object of the correct type for the given reference
   * to an annotation dictionary. This yields a promise that is resolved when
   * the `Annotation` object is constructed.
   *
   * @param {XRef} xref
   * @param {Object} ref
   * @param {PDFManager} pdfManager
   * @param {Object} idFactory
   * @returns {Promise} A promise that is resolved with an {Annotation}
   *   instance.
   */
  static create(xref, ref, pdfManager, idFactory) {
    return pdfManager.ensureCatalog("acroForm").then(acroForm => {
      return pdfManager.ensure(this, "_create", [
        xref,
        ref,
        pdfManager,
        idFactory,
        acroForm,
      ]);
    });
  }
  /**
   * @private
   */
  static _create(xref, ref, pdfManager, idFactory, acroForm) {