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 pageView = this._pages[this._currentPageNumber - 1];
    if (this.isInPresentationMode) {
      
      this._setScale(this._currentScaleValue, true);
    }
    this.#scrollIntoView(pageView);
  }
  /**
   * @param {string} label - The page label.
   * @returns {number|null} The page number corresponding to the page label,
   *   or `null` when no page labels exist and/or the input is invalid.
   */
  pageLabelToPageNumber(label) {