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.pdfHistory) {
      return;
    }
    this.pdfHistory.initialize({
      fingerprint,
      resetHistory: viewOnLoad === ViewOnLoad.INITIAL,
      updateUrl: AppOptions.get("historyUpdateUrl"),
    });
    if (this.pdfHistory.initialBookmark) {
      this.initialBookmark = this.pdfHistory.initialBookmark;
      this.initialRotation = this.pdfHistory.initialRotation;
    }
    
    if (
      initialDest &&
      !this.initialBookmark &&
      viewOnLoad === ViewOnLoad.UNKNOWN
    ) {
      this.initialBookmark = JSON.stringify(initialDest);
      
      
      this.pdfHistory.push({ explicitDest: initialDest, pageNumber: null });
    }
  },
  /**
   * @private
   */
  _initializeAnnotationStorageCallbacks(pdfDocument) {