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 (!this.pdfDocument) {
      return;
    }
    let page = val | 0; 
    if (this._pageLabels) {
      const i = this._pageLabels.indexOf(val);
      if (i >= 0) {
        page = i + 1;
      }
    }
    
    if (!this._setCurrentPageNumber(page,  true)) {
      console.error(`currentPageLabel: "${val}" is not a valid page.`);
    }
  }
  /**
   * @type {number}
   */
  get currentScale() {
    return this._currentScale !== UNKNOWN_SCALE
      ? this._currentScale
      : DEFAULT_SCALE;
  }
  /**
   * @param {number} val - Scale of the pages in percents.
   */
  set currentScale(val) {