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.pdfViewer.presentationModeState = evt.state;
}
function webViewerSidebarViewChanged({ view }) {
  PDFViewerApplication.pdfRenderingQueue.isThumbnailViewEnabled =
    view === SidebarView.THUMBS;
  if (PDFViewerApplication.isInitialViewSet) {
    
    PDFViewerApplication.store?.set("sidebarView", view).catch(() => {
      
    });
  }
}
function webViewerUpdateViewarea({ location }) {