get hasEqualPageSizes() {
    const firstPageView = this._pages[0];
    for (let i = 1, ii = this._pages.length; i < ii; ++i) {
      const pageView = this._pages[i];
      if (
        pageView.width !== firstPageView.width ||
        pageView.height !== firstPageView.height
      ) {
        return false;
      }
    }
    return true;
  }
@type {boolean} Whether all pages of the PDF document have identical
  widths and heights.