We could use:
https://github.com/mozilla/pdf.js/blob/c3d08580627471432a6ad0b2fdb948df64126afa/src/display/api.js#L929

and look at bit 4.

The following pdf:
https://orimi.com/pdf-test.pdf
is not editable in neither Acrobat nor Edge nor Foxit and nor Okular.
return new TextHighlighter({
      eventBus,
      pageIndex,
      findController: this.isInPresentationMode ? null : this.findController,
    });
  }
  /**
   * @param {HTMLDivElement} pageDiv
   * @param {PDFPageProxy} pdfPage
   * @param {AnnotationStorage} [annotationStorage] - Storage for annotation
   *   data in forms.
   * @param {string} [imageResourcesPath] - Path for image resources, mainly
   *   for annotation icons. Include trailing slash.
   * @param {boolean} renderForms
   * @param {IL10n} l10n
   * @param {boolean} [enableScripting]
   * @param {Promise<boolean>} [hasJSActionsPromise]
   * @param {Object} [mouseState]
   * @param {Promise<Object<string, Array<Object>> | null>}
   *   [fieldObjectsPromise]
   * @param {Map<string, HTMLCanvasElement>} [annotationCanvasMap]
   * @returns {AnnotationLayerBuilder}
   */
  createAnnotationLayerBuilder(