previousPage() {
    const currentPageNumber = this._currentPageNumber;

    if (currentPageNumber <= 1) {
      return false;
    }
    const advance =
      this._getPageAdvance(currentPageNumber, /* previous = */ true) || 1;

    this.currentPageNumber = Math.max(currentPageNumber - advance, 1);
    return true;
  }
Go to the previous page, taking scroll/spread-modes into account.
@returns {boolean} Whether navigation occurred.