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.
const visiblePages = currentlyVisiblePages || this._getVisiblePages();
    const scrollAhead = this.#getScrollAhead(visiblePages);
    const preRenderExtra =
      this._spreadMode !== SpreadMode.NONE &&
      this._scrollMode !== ScrollMode.HORIZONTAL;
    const pageView = this.renderingQueue.getHighestPriority(
      visiblePages,
      this._pages,
      scrollAhead,
      preRenderExtra
    );
    this.#toggleLoadingIconSpinner(visiblePages.ids);
    if (pageView) {
      this.#ensurePdfPageLoaded(pageView).then(() => {
        this.renderingQueue.renderView(pageView);
      });
      return true;
    }
    return false;
  }
  /**
   * @param {HTMLDivElement} textLayerDiv
   * @param {number} pageIndex
   * @param {PageViewport} viewport
   * @param {boolean} enhanceTextSelection
   * @param {EventBus} eventBus
   * @param {TextHighlighter} highlighter
   * @returns {TextLayerBuilder}
   */
  createTextLayerBuilder(