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.
* @private
   */
  async _readPreferences() {
    if (
      typeof PDFJSDev === "undefined" ||
      PDFJSDev.test("!PRODUCTION || GENERIC")
    ) {
      if (AppOptions.get("disablePreferences")) {
        
        
        return;
      }
      if (AppOptions._hasUserOptions()) {
        console.warn(
          "_readPreferences: The Preferences may override manually set AppOptions; " +
            'please use the "disablePreferences"-option in order to prevent that.'
        );
      }
    }
    try {
      AppOptions.setAll(await this.preferences.getAll());
    } catch (reason) {
      console.error(`_readPreferences: "${reason?.message}".`);
    }
  },
  /**
   * Potentially parse special debugging flags in the hash section of the URL.
   * @private
   */
  async _parseHashParameters() {