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.
if (visible.first?.id === 1) {
      return true;
    } else if (visible.last?.id === this.pagesCount) {
      return false;
    }
    switch (this._scrollMode) {
      case ScrollMode.PAGE:
        return this.#scrollModePageState.scrollDown;
      case ScrollMode.HORIZONTAL:
        return this.scroll.right;
    }
    return this.scroll.down;
  }
  /**
   * Only show the `loadingIcon`-spinner on visible pages (see issue 14242).
   */
  #toggleLoadingIconSpinner(visibleIds) {
    for (const id of visibleIds) {
      const pageView = this._pages[id - 1];
      pageView?.toggleLoadingIconSpinner( true);
    }
    for (const pageView of this.#buffer) {
      if (visibleIds.has(pageView.id)) {
        
        continue;
      }
      pageView.toggleLoadingIconSpinner( false);
    }
  }
  forceRendering(currentlyVisiblePages) {