diff --git a/src/PDFJSAnnotate.js b/src/PDFJSAnnotate.js
index 77e0cc9e..9bdfa6ca 100644
--- a/src/PDFJSAnnotate.js
+++ b/src/PDFJSAnnotate.js
@@ -78,7 +78,7 @@ export default {
    * @param {String} pageNumber The page number
    * @return {Promise}
    */
-  getAnnotations(documentId, pageNumber) {
+  getAnnotations(documentId, userId, pageNumber) {
     return this.getStoreAdapter().getAnnotations(...arguments);
   },
 
diff --git a/src/UI/arrow.js b/src/UI/arrow.js
index 8dbf4213..b8e66b1c 100644
--- a/src/UI/arrow.js
+++ b/src/UI/arrow.js
@@ -33,11 +33,11 @@ function handleDocumentMousedown(e) {
   }
 
   let svg = findSVGContainer(target);
-  let { documentId } = getMetadata(svg);
+  let { documentId, userId } = getMetadata(svg);
   let annotationId = target.getAttribute('data-pdf-annotate-id');
 
   let event = e;
-  PDFJSAnnotate.getStoreAdapter().getAnnotation(documentId, annotationId).then((annotation) => {
+  PDFJSAnnotate.getStoreAdapter().getAnnotation(documentId, userId, annotationId).then((annotation) => {
     if (annotation) {
       path = null;
       lines = [];
diff --git a/src/UI/circle.js b/src/UI/circle.js
index bf211cb9..f880b1ce 100644
--- a/src/UI/circle.js
+++ b/src/UI/circle.js
@@ -59,10 +59,10 @@ function saveCircle(svg, type, pt, radius, color) {
     r: radius
   };
 
-  let { documentId, pageNumber } = getMetadata(svg);
+  let { documentId, userId, pageNumber } = getMetadata(svg);
 
   // Add the annotation
-  PDFJSAnnotate.getStoreAdapter().addAnnotation(documentId, pageNumber, annotation)
+  PDFJSAnnotate.getStoreAdapter().addAnnotation(documentId, userId, pageNumber, annotation)
     .then((annotation) => {
       appendChild(svg, annotation);
     });
diff --git a/src/UI/edit.js b/src/UI/edit.js
index dc74ecaf..7ef7e432 100644
--- a/src/UI/edit.js
+++ b/src/UI/edit.js
@@ -225,11 +225,11 @@ function handleDocumentMouseup(e) {
   let target = document.querySelectorAll(`[data-pdf-annotate-id="${annotationId}"]`);
   let type = target[0].getAttribute('data-pdf-annotate-type');
   let svg = overlay.parentNode.querySelector(config.annotationSvgQuery());
-  let { documentId } = getMetadata(svg);
+  let { documentId, userId } = getMetadata(svg);
   
   overlay.querySelector('a').style.display = '';
 
-  PDFJSAnnotate.getStoreAdapter().getAnnotation(documentId, annotationId).then((annotation) => {
+  PDFJSAnnotate.getStoreAdapter().getAnnotation(documentId, userId, annotationId).then((annotation) => {
     let attribX = 'x';
     let attribY = 'y';
     if (['circle', 'fillcircle', 'emptycircle'].indexOf(type) > -1) {
diff --git a/src/UI/eraser.js b/src/UI/eraser.js
index e9515d15..a9f4b143 100644
--- a/src/UI/eraser.js
+++ b/src/UI/eraser.js
@@ -19,7 +19,7 @@ function handleDocumentMouseMove(e){
     let target = findAnnotationAtPoint(e.clientX, e.clientY);
     if(target){
       console.log(target);
-      let annotationId = target.getAttribute('data-pdf-annotate-id');
+      // let annotationId = target.getAttribute('data-pdf-annotate-id');
       // let nodes = document.querySelectorAll(`[data-pdf-annotate-id="${annotationId}"]`);
       // let svg = overlay.parentNode.querySelector(config.annotationSvgQuery());
       // let { documentId } = getMetadata(svg);
diff --git a/src/UI/page.js b/src/UI/page.js
index 717c0d0d..0a54b4e0 100644
--- a/src/UI/page.js
+++ b/src/UI/page.js
@@ -48,6 +48,7 @@ export function createPage(pageNumber) {
 export function renderPage(pageNumber, renderOptions) {
   let {
     documentId,
+    userId,
     pdfDocument,
     scale,
     rotate
@@ -56,7 +57,7 @@ export function renderPage(pageNumber, renderOptions) {
   // Load the page and annotations
   return Promise.all([
     pdfDocument.getPage(pageNumber),
-    PDFJSAnnotate.getAnnotations(documentId, pageNumber)
+    PDFJSAnnotate.getAnnotations(documentId, userId, pageNumber)
   ]).then(([pdfPage, annotations]) => {
     let page = document.getElementById(`pageContainer${pageNumber}`);
     let svg = page.querySelector(config.annotationClassQuery());
diff --git a/src/UI/pen.js b/src/UI/pen.js
index 85bede78..a323e98c 100644
--- a/src/UI/pen.js
+++ b/src/UI/pen.js
@@ -41,9 +41,8 @@ function saveToStorage(x, y){
   _candraw = false;
   let svg;
   if (lines.length > 1 && (svg = findSVGAtPoint(x, y))) {
-    let { documentId, pageNumber } = getMetadata(svg);
-
-    PDFJSAnnotate.getStoreAdapter().addAnnotation(documentId, pageNumber, {
+    let { documentId, userId, pageNumber } = getMetadata(svg);
+    PDFJSAnnotate.getStoreAdapter().addAnnotation(documentId, userId, pageNumber, {
         type: 'drawing',
         width: _penSize,
         color: _penColor,
diff --git a/src/UI/point.js b/src/UI/point.js
index fb5da3f6..cde303f3 100644
--- a/src/UI/point.js
+++ b/src/UI/point.js
@@ -70,7 +70,7 @@ function savePoint() {
     }
 
     let rect = svg.getBoundingClientRect();
-    let { documentId, pageNumber } = getMetadata(svg);
+    let { documentId, userId, pageNumber } = getMetadata(svg);
     let annotation = Object.assign({
         type: 'point'
       }, scaleDown(svg, {
@@ -79,7 +79,7 @@ function savePoint() {
       })
     );
 
-    PDFJSAnnotate.getStoreAdapter().addAnnotation(documentId, pageNumber, annotation)
+    PDFJSAnnotate.getStoreAdapter().addAnnotation(documentId, userId, pageNumber, annotation)
       .then((annotation) => {
         PDFJSAnnotate.getStoreAdapter().addComment(
           documentId,
diff --git a/src/UI/rect.js b/src/UI/rect.js
index 0f1b9c4f..fa7c2af3 100644
--- a/src/UI/rect.js
+++ b/src/UI/rect.js
@@ -195,10 +195,10 @@ function saveRect(type, rects, color) {
     annotation.height = rect.height;
   }
 
-  let { documentId, pageNumber } = getMetadata(svg);
+  let { documentId, userId, pageNumber } = getMetadata(svg);
 
   // Add the annotation
-  PDFJSAnnotate.getStoreAdapter().addAnnotation(documentId, pageNumber, annotation)
+  PDFJSAnnotate.getStoreAdapter().addAnnotation(documentId, userId, pageNumber, annotation)
     .then((annotation) => {
       appendChild(svg, annotation);
     });
diff --git a/src/UI/text.js b/src/UI/text.js
index 120b39d8..e571f276 100644
--- a/src/UI/text.js
+++ b/src/UI/text.js
@@ -71,7 +71,7 @@ function saveText() {
       return;
     }
     let height = _textSize;
-    let { documentId, pageNumber, viewport } = getMetadata(svg);
+    let { documentId, userId, pageNumber, viewport } = getMetadata(svg);
     let scale = 1 / viewport.scale;
     let rect = svg.getBoundingClientRect();
     let pt = convertToSvgPoint([
@@ -87,7 +87,7 @@ function saveText() {
         rotation: -viewport.rotation
     }
 
-    PDFJSAnnotate.getStoreAdapter().addAnnotation(documentId, pageNumber, annotation)
+    PDFJSAnnotate.getStoreAdapter().addAnnotation(documentId, userId, pageNumber, annotation)
       .then((annotation) => {
         appendChild(svg, annotation);
       });
diff --git a/src/UI/utils.js b/src/UI/utils.js
index e8078765..fd59d3b2 100644
--- a/src/UI/utils.js
+++ b/src/UI/utils.js
@@ -264,6 +264,7 @@ export function enableUserSelect() {
 export function getMetadata(svg) {
   return {
     documentId: svg.getAttribute('data-pdf-annotate-document'),
+    userId: svg.getAttribute('data-pdf-annotate-user'),
     pageNumber: parseInt(svg.getAttribute('data-pdf-annotate-page'), 10),
     viewport: JSON.parse(svg.getAttribute('data-pdf-annotate-viewport'))
   };
diff --git a/src/a11y/initEventHandlers.js b/src/a11y/initEventHandlers.js
index f0243daa..b5d15127 100644
--- a/src/a11y/initEventHandlers.js
+++ b/src/a11y/initEventHandlers.js
@@ -9,11 +9,11 @@ import PDFJSAnnotate from '../PDFJSAnnotate';
  * Initialize the event handlers for keeping screen reader hints synced with data
  */
 export default function initEventHandlers() {
-  addEventListener('annotation:add', (documentId, pageNumber, annotation) => {
-    reorderAnnotationsByType(documentId, pageNumber, annotation.type);
+  addEventListener('annotation:add', (documentId, userId, pageNumber, annotation) => {
+    reorderAnnotationsByType(documentId, userId, pageNumber, annotation.type);
   });
-  addEventListener('annotation:edit', (documentId, annotationId, annotation) => {
-    reorderAnnotationsByType(documentId, annotation.page, annotation.type);
+  addEventListener('annotation:edit', (documentId, userId, annotationId, annotation) => {
+    reorderAnnotationsByType(documentId, userId, annotation.page, annotation.type);
   });
   addEventListener('annotation:delete', removeAnnotation);
   addEventListener('comment:add', insertComment);
@@ -24,11 +24,12 @@ export default function initEventHandlers() {
  * Reorder the annotation numbers by annotation type
  *
  * @param {String} documentId The ID of the document
+ * @param {String} userId The ID of the user
  * @param {Number} pageNumber The page number of the annotations
  * @param {Strig} type The annotation type
  */
-function reorderAnnotationsByType(documentId, pageNumber, type) {
-  PDFJSAnnotate.getStoreAdapter().getAnnotations(documentId, pageNumber)
+function reorderAnnotationsByType(documentId, userId, pageNumber, type) {
+  PDFJSAnnotate.getStoreAdapter().getAnnotations(documentId, userId, pageNumber)
     .then((annotations) => {
       return annotations.annotations.filter((a) => {
         return a.type === type;
diff --git a/src/adapter/LocalStoreAdapter.js b/src/adapter/LocalStoreAdapter.js
index 72a04c89..2cb6f0c8 100644
--- a/src/adapter/LocalStoreAdapter.js
+++ b/src/adapter/LocalStoreAdapter.js
@@ -6,70 +6,71 @@ import StoreAdapter from './StoreAdapter';
 export default class LocalStoreAdapter extends StoreAdapter {
   constructor() {
     super({
-      getAnnotations(documentId, pageNumber) {
+      getAnnotations(documentId, userId, pageNumber) {
         return new Promise((resolve, reject) => {
-          let annotations = getAnnotations(documentId).filter((i) => {
+          let annotations = getAnnotations(documentId, userId).filter((i) => {
             return i.page === pageNumber && i.class === 'Annotation';
           });
 
           resolve({
             documentId,
+            userId,
             pageNumber,
             annotations
           });
         });
       },
 
-      getAnnotation(documentId, annotationId) {
-        return Promise.resolve(getAnnotations(documentId)[findAnnotation(documentId, annotationId)]);
+      getAnnotation(documentId, userId, annotationId) {
+        return Promise.resolve(getAnnotations(documentId, userId)[findAnnotation(documentId, userId, annotationId)]);
       },
 
-      addAnnotation(documentId, pageNumber, annotation) {
+      addAnnotation(documentId, userId, pageNumber, annotation) {
         return new Promise((resolve, reject) => {
           annotation.class = 'Annotation';
           annotation.uuid = uuid();
           annotation.page = pageNumber;
 
-          let annotations = getAnnotations(documentId);
+          let annotations = getAnnotations(documentId, userId);
           annotations.push(annotation);
-          updateAnnotations(documentId, annotations);
+          updateAnnotations(documentId, userId, annotations);
 
           resolve(annotation);
         });
       },
 
-      editAnnotation(documentId, annotationId, annotation) {
+      editAnnotation(documentId, userId, annotationId, annotation) {
         return new Promise((resolve, reject) => {
-          let annotations = getAnnotations(documentId);
-          annotations[findAnnotation(documentId, annotationId)] = annotation;
-          updateAnnotations(documentId, annotations);
+          let annotations = getAnnotations(documentId, userId);
+          annotations[findAnnotation(documentId, userId, annotationId)] = annotation;
+          updateAnnotations(documentId, userId, annotations);
 
           resolve(annotation);
         });
       },
 
-      deleteAnnotation(documentId, annotationId) {
+      deleteAnnotation(documentId, userId, annotationId) {
         return new Promise((resolve, reject) => {
-          let index = findAnnotation(documentId, annotationId);
+          let index = findAnnotation(documentId, userId, annotationId);
           if (index > -1) {
-            let annotations = getAnnotations(documentId);
+            let annotations = getAnnotations(documentId, userId);
             annotations.splice(index, 1);
-            updateAnnotations(documentId, annotations);
+            updateAnnotations(documentId, userId, annotations);
           }
 
           resolve(true);
         });
       },
 
-      getComments(documentId, annotationId) {
+      getComments(documentId, userId, annotationId) {
         return new Promise((resolve, reject) => {
-          resolve(getAnnotations(documentId).filter((i) => {
+          resolve(getAnnotations(documentId, userId).filter((i) => {
             return i.class === 'Comment' && i.annotation === annotationId;
           }));
         });
       },
 
-      addComment(documentId, annotationId, content) {
+      addComment(documentId, userId, annotationId, content) {
         return new Promise((resolve, reject) => {
           let comment = {
             class: 'Comment',
@@ -78,19 +79,19 @@ export default class LocalStoreAdapter extends StoreAdapter {
             content: content
           };
 
-          let annotations = getAnnotations(documentId);
+          let annotations = getAnnotations(documentId, userId);
           annotations.push(comment);
-          updateAnnotations(documentId, annotations);
+          updateAnnotations(documentId, userId, annotations);
 
           resolve(comment);
         });
       },
 
-      deleteComment(documentId, commentId) {
+      deleteComment(documentId, userId, commentId) {
         return new Promise((resolve, reject) => {
-          getAnnotations(documentId);
+          getAnnotations(documentId, userId);
           let index = -1;
-          let annotations = getAnnotations(documentId);
+          let annotations = getAnnotations(documentId, userId);
           for (let i=0, l=annotations.length; i<l; i++) {
             if (annotations[i].uuid === commentId) {
               index = i;
@@ -100,7 +101,7 @@ export default class LocalStoreAdapter extends StoreAdapter {
 
           if (index > -1) {
             annotations.splice(index, 1);
-            updateAnnotations(documentId, annotations);
+            updateAnnotations(documentId, userId, annotations);
           }
 
           resolve(true);
@@ -110,17 +111,17 @@ export default class LocalStoreAdapter extends StoreAdapter {
   }
 }
 
-function getAnnotations(documentId) {
-  return JSON.parse(localStorage.getItem(`${documentId}/annotations`)) || [];
+function getAnnotations(documentId, userId) {
+  return JSON.parse(localStorage.getItem(`${documentId}/${userId}/annotations`)) || [];
 }
-
-function updateAnnotations(documentId, annotations) {
-  localStorage.setItem(`${documentId}/annotations`, JSON.stringify(annotations));
+// Note, userId should not be an optional parameter, leaving it here for debugging purposes
+function updateAnnotations(documentId, userId='bitdiddle', annotations) {
+  localStorage.setItem(`${documentId}/${userId}/annotations`, JSON.stringify(annotations));
 }
 
-function findAnnotation(documentId, annotationId) {
+function findAnnotation(documentId, userId, annotationId) {
   let index = -1;
-  let annotations = getAnnotations(documentId);
+  let annotations = getAnnotations(documentId, userId);
   for (let i=0, l=annotations.length; i<l; i++) {
     if (annotations[i].uuid === annotationId) {
       index = i;
diff --git a/src/adapter/StoreAdapter.js b/src/adapter/StoreAdapter.js
index 7f2a21c7..eef48dbc 100644
--- a/src/adapter/StoreAdapter.js
+++ b/src/adapter/StoreAdapter.js
@@ -25,10 +25,10 @@ export default class StoreAdapter {
    * @param {Number} pageNumber The number of the page the annotations belong to
    * @return {Promise}
    */
-  __getAnnotations(documentId, pageNumber) { abstractFunction('getAnnotations'); }
+  __getAnnotations(documentId, userId, pageNumber) { abstractFunction('getAnnotations'); }
   get getAnnotations() { return this.__getAnnotations; }
   set getAnnotations(fn) {
-    this.__getAnnotations = function getAnnotations(documentId, pageNumber) {
+    this.__getAnnotations = function getAnnotations(documentId, userId, pageNumber) {
       return fn(...arguments).then((annotations) => {
         // TODO may be best to have this happen on the server
         if (annotations.annotations) {
@@ -58,12 +58,12 @@ export default class StoreAdapter {
    * @param {Object} annotation The definition for the new annotation
    * @return {Promise}
    */
-  __addAnnotation(documentId, pageNumber, annotation) { abstractFunction('addAnnotation'); }
+  __addAnnotation(documentId, userId, pageNumber, annotation) { abstractFunction('addAnnotation'); }
   get addAnnotation() { return this.__addAnnotation; }
   set addAnnotation(fn) {
-    this.__addAnnotation = function addAnnotation(documentId, pageNumber, annotation) {
+    this.__addAnnotation = function addAnnotation(documentId, userId, pageNumber, annotation) {
       return fn(...arguments).then((annotation) => {
-        fireEvent('annotation:add', documentId, pageNumber, annotation);
+        fireEvent('annotation:add', documentId, userId, pageNumber, annotation);
         return annotation;
       });
     };
diff --git a/src/render/index.js b/src/render/index.js
index acce9d2a..3262fb4d 100644
--- a/src/render/index.js
+++ b/src/render/index.js
@@ -28,6 +28,7 @@ export default function render(svg, viewport, data) {
     }
 
     svg.setAttribute('data-pdf-annotate-document', data.documentId);
+    svg.setAttribute('data-pdf-annotate-user', data.userId);
     svg.setAttribute('data-pdf-annotate-page', data.pageNumber);
   
     // Make sure annotations is an array
diff --git a/web/index.js b/web/index.js
index 548d2bd6..a0a51933 100644
--- a/web/index.js
+++ b/web/index.js
@@ -7,6 +7,7 @@ const documentId = 'example.pdf';
 let PAGE_HEIGHT;
 let RENDER_OPTIONS = {
   documentId,
+  userId: 'aphacker',
   pdfDocument: null,
   scale: parseFloat(localStorage.getItem(`${documentId}/scale`), 10) || 1.33,
   rotate: parseInt(localStorage.getItem(`${documentId}/rotate`), 10) || 0
@@ -383,7 +384,7 @@ render();
         document.querySelector(`div#pageContainer${i+1} svg.annotationLayer`).innerHTML = '';
       }
 
-      localStorage.removeItem(`${RENDER_OPTIONS.documentId}/annotations`);
+      localStorage.removeItem(`${RENDER_OPTIONS.documentId}/${RENDER_OPTIONS.userId}/annotations`);
     }
   }
   document.querySelector('a.clear').addEventListener('click', handleClearClick);