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.zoomReset();
}
function webViewerPageNumberChanged(evt) {
  const pdfViewer = PDFViewerApplication.pdfViewer;
  
  
  if (evt.value !== "") {
    PDFViewerApplication.pdfLinkService.goToPage(evt.value);
  }
  
  
  if (
    evt.value !== pdfViewer.currentPageNumber.toString() &&
    evt.value !== pdfViewer.currentPageLabel
  ) {
    PDFViewerApplication.toolbar.setPageNumber(
      pdfViewer.currentPageNumber,
      pdfViewer.currentPageLabel
    );
  }
}
function webViewerScaleChanged(evt) {
  PDFViewerApplication.pdfViewer.currentScaleValue = evt.value;
}
function webViewerRotateCw() {
  PDFViewerApplication.rotatePages(90);
}
function webViewerRotateCcw() {