Prevent editing signed PDF

function getViewerOptions() {
	return { 
		workerSrc: "/document-solutions/javascript-pdf-viewer/demos/product-bundles/build/dspdfviewer.worker.js",
		supportApi: {
			apiUrl: window.top.SUPPORTAPI_URL, token: window.top.SUPPORTAPI_TOKEN, webSocketUrl: false
		}
	};		
}

function configureViewerUI(viewer) {
	var documentSigned = false;
	viewer.addDefaultPanels();
	viewer.addAnnotationEditorPanel();
	viewer.addFormEditorPanel();
	viewer.onAfterOpen.register(function() {
		viewer.getSignatureInfo().then(function (info) {
			documentSigned = info.signed;
		});		
	});
	// Cancel edit events if the current document is electronically signed:
	const onBeforeEditHandler = (args) => {
        const cancel = documentSigned && args.annotation.annotationType !== 13 /* Allow editing stamps */;
        if(cancel) {
		  args.cancel = true;
          setTimeout(()=> { 
              viewer.showMessage("Cannot edit a signed document.", "The document was signed with an electronic digital signature.", "warn");
			  viewer.hideSecondToolbar();
              viewer.layoutMode = 0;
              viewer.editMode = 0; 
              viewer.repaint(); 
          }, 200);
        }
	};
	viewer.onBeforeAddAnnotation.register(onBeforeEditHandler);
	viewer.onBeforeUpdateAnnotation.register(onBeforeEditHandler);
	viewer.onBeforeRemoveAnnotation.register(onBeforeEditHandler);
}
window.onload = function() {
    var viewer = new DsPdfViewer("#viewer", getViewerOptions());
	configureViewerUI(viewer);
	viewer.open("/document-solutions/javascript-pdf-viewer/demos/product-bundles/assets/pdf/prevent-editing-signed-pdf.pdf");
}