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 (isNaN(val)) {
      throw new Error("Invalid numeric scale.");
    }
    if (!this.pdfDocument) {
      return;
    }
    this._setScale(val, false);
  }
  /**
   * @type {string}
   */
  get currentScaleValue() {
    return this._currentScaleValue;
  }
  /**
   * @param val - The scale of the pages (in percent or predefined value).
   */
  set currentScaleValue(val) {
    if (!this.pdfDocument) {
      return;
    }
    this._setScale(val, false);
  }
  /**
   * @type {number}
   */
  get pagesRotation() {