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.
return this._pages.map(pageView => {
      const viewport = pageView.pdfPage.getViewport({ scale: 1 });
      if (!this.enablePrintAutoRotate || isPortraitOrientation(viewport)) {
        return {
          width: viewport.width,
          height: viewport.height,
          rotation: viewport.rotation,
        };
      }
      
      return {
        width: viewport.height,
        height: viewport.width,
        rotation: (viewport.rotation - 90) % 360,
      };
    });
  }
  /**
   * @type {Promise<OptionalContentConfig | null>}
   */
  get optionalContentConfigPromise() {