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.
PDFViewerApplication.requestPresentationMode();
}
function webViewerSwitchAnnotationEditorMode(evt) {
  PDFViewerApplication.pdfViewer.annotationEditorMode = evt.mode;
}
function webViewerPrint() {