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.
};
    _boundEvents.windowBeforePrint = () => {
      eventBus.dispatch("beforeprint", { source: window });
    };
    _boundEvents.windowAfterPrint = () => {
      eventBus.dispatch("afterprint", { source: window });
    };
    _boundEvents.windowUpdateFromSandbox = event => {
      eventBus.dispatch("updatefromsandbox", {
        source: window,
        detail: event.detail,
      });
    };
    window.addEventListener("visibilitychange", webViewerVisibilityChange);
    window.addEventListener("wheel", webViewerWheel, { passive: false });
    window.addEventListener("touchstart", webViewerTouchStart, {
      passive: false,
    });
    window.addEventListener("click", webViewerClick);
    window.addEventListener("keydown", webViewerKeyDown);
    window.addEventListener("resize", _boundEvents.windowResize);
    window.addEventListener("hashchange", _boundEvents.windowHashChange);
    window.addEventListener("beforeprint", _boundEvents.windowBeforePrint);
    window.addEventListener("afterprint", _boundEvents.windowAfterPrint);
    window.addEventListener(
      "updatefromsandbox",
      _boundEvents.windowUpdateFromSandbox
    );
  },
  unbindEvents() {