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 (this.isViewerEmbedded) {
      
      return;
    }
    document.title = title;
  },
  get _docFilename() {
    
    
    return this._contentDispositionFilename || getPdfFilenameFromUrl(this.url);
  },
  /**
   * @private
   */
  _hideViewBookmark() {