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.
GlobalWorkerOptions.workerSrc ||= AppOptions.get("workerSrc");
  if (typeof PDFJSDev === "undefined" || !PDFJSDev.test("PRODUCTION")) {
    window.pdfjsWorker = await import("pdfjs/core/worker.js");
    return;
  }
  await loadScript(PDFWorker.workerSrc);
}
async function loadPDFBug(self) {
  const { debuggerScriptPath } = self.appConfig;
  const { PDFBug } =
    typeof PDFJSDev === "undefined" || !PDFJSDev.test("PRODUCTION")
      ? await import(debuggerScriptPath) 
      : await __non_webpack_import__(debuggerScriptPath); 
  self._PDFBug = PDFBug;
}
function reportPageStatsPDFBug({ pageNumber }) {
  if (!globalThis.Stats?.enabled) {
    return;
  }
  const pageView = PDFViewerApplication.pdfViewer.getPageView(
     pageNumber - 1
  );
  globalThis.Stats.add(pageNumber, pageView?.pdfPage?.stats);
}
function webViewerInitialized() {