test.js

function storeAnnotations() {

  var annotations = TXDocumentViewer.annotations.export();

  var obj = JSON.parse(annotations);
  var serviceURL = '@Url.Action("MergeAnnotations", "Home")';

  $.ajax({
    type: 'POST',
    url: serviceURL,
    contentType: 'application/json',
    dataType: 'json',
    data: JSON.stringify(obj),
    success: successFunc,
    error: errorFunc
  });

  function successFunc(data, status) {
    TXDocumentViewer.loadDocument(data.data, 'results.tx');
  }
  
  function errorFunc() {
    alert('error');
  }

}