How to save and retrieve the annotations from the database?

<div style="float:right; height:780px;width:30% ; border: solid black 1px; top:3px;" id="Annotations">
        <h2> Annotations List </h2>
    </div>
    <div class="content-container-fluid">
        <div style="width:69.5%;height:780px;">
            <button id="button1" type="button" onclick="annotationsOperation(event)">Save Annotations</button>
            <button id="button2" type="button" onclick="showAnnotation(event)">Show Annotations</button>
            @(Html.EJ().PdfViewer("pdfviewer").ServiceUrl("../api/PdfViewer"))
        </div>       
        </div>    
 

function showAnnotation(event)
            {
                $.ajax({
                    type: 'POST',
                    url: '../api/PdfViewer/ReadID',
                    crossDomain: true,
                    contentType: 'application/json; charset=utf-8',
                    dataType: 'json',
                    data: null,
                    traditional: true,
                    success: function (data) {
                        var annotations = data;
                        var annotdiv = document.getElementById('Annotations');
                        var annotlist = document.getElementById('Annotationlist');
                        if (annotlist != null)
                        {
                            annotlist.remove();
                        }
                        var ul = document.createElement('ul');
                        ul.id = "Annotationlist";
                        for (var a = 0; a < annotations.length ; a++) {
                            var li = document.createElement('li');
                            li.innerHTML = annotations[a];
                            li.onclick = function (event) {
                                var id = event.currentTarget.innerHTML;
                                var jsonResult = new Object();
                                var jsonObject = { Id: event.currentTarget.innerHTML };
                                $.ajax({
                                    type: 'POST',
                                    url: '../api/PdfViewer/RetriveAnnotation',
                                    crossDomain: true,
                                    contentType: 'application/json; charset=utf-8',
                                    dataType: 'json',
                                    data: JSON.stringify(jsonObject),
                                    traditional: true,
                                    success: function (data) {
                                        var obj = $("#pdfviewer").data("ejPdfViewer");
                                        var base64 = "data:application/pdf;base64," + data["documentStream"];
                                      obj.load(base64);
                                    }
                                });                              
                            };
                            ul.appendChild(li);
                        }
                        annotdiv.appendChild(ul);
                    }
                });                       
            };
 
            function annotationsOperation(event) {
                var pdfviewer = $("#pdfviewer").data("ejPdfViewer");
                pdfviewer.model.serverActionSettings.download = "DocumentRetrieve";
                pdfviewer.download(false);
                pdfviewer.model.serverActionSettings.download = "Download";
                alert("Annotations saved in Database");     
            }