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 (PDFViewerApplication.isInitialViewSet) {
    
    PDFViewerApplication.store?.set("scrollMode", evt.mode).catch(() => {
      
    });
  }
}
function webViewerSpreadModeChanged(evt) {