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 currentScale = this._currentScale;
    const currentScaleValue = this._currentScaleValue;
    const normalizedScaleValue =
      parseFloat(currentScaleValue) === currentScale
        ? Math.round(currentScale * 10000) / 100
        : currentScaleValue;
    const pageNumber = firstPage.id;
    const currentPageView = this._pages[pageNumber - 1];
    const container = this.container;
    const topLeft = currentPageView.getPagePoint(
      container.scrollLeft - firstPage.x,
      container.scrollTop - firstPage.y
    );
    const intLeft = Math.round(topLeft[0]);
    const intTop = Math.round(topLeft[1]);
    let pdfOpenParams = `#page=${pageNumber}`;
    if (!this.isInPresentationMode) {
      pdfOpenParams += `&zoom=${normalizedScaleValue},${intLeft},${intTop}`;
    }
    this._location = {
      pageNumber,
      scale: normalizedScaleValue,
      top: intTop,
      left: intLeft,
      rotation: this._pagesRotation,
      pdfOpenParams,
    };
  }
  update() {