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.
const hash = evt.hash;
  if (!hash) {
    return;
  }
  if (!PDFViewerApplication.isInitialViewSet) {
    PDFViewerApplication.initialBookmark = hash;
  } else if (!PDFViewerApplication.pdfHistory?.popStateInProgress) {
    PDFViewerApplication.pdfLinkService.setHash(hash);
  }
}
if (typeof PDFJSDev === "undefined" || PDFJSDev.test("GENERIC")) {
  
  var webViewerFileInputChange = function (evt) {
    if (PDFViewerApplication.pdfViewer?.isInPresentationMode) {
      return; 
    }
    const file = evt.fileInput.files[0];
    let url = URL.createObjectURL(file);
    if (file.name) {
      url = { url, originalUrl: file.name };
    }
    PDFViewerApplication.open(url);
  };
  
  var webViewerOpenFile = function (evt) {
    const fileInput = PDFViewerApplication.appConfig.openFileInput;
    fileInput.click();
  };
}
function webViewerPresentationMode() {