diff --git a/CHANGELOG b/CHANGELOG
index e3b117329..b699a1815 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -48,6 +48,9 @@ Core:
 - Enhanced performance esp. for server restart and first connection of all
   clients by refactorting autoupdate, Collection and AccessPermission [#3223].
 
+Mediafiles:
+- Fixed reloading of PDF on page change [#3274]
+
 General:
 - Switched from npm to Yarn [#3188].
 - Several bugfixes and minor improvements.
diff --git a/openslides/core/static/js/core/projector.js b/openslides/core/static/js/core/projector.js
index 8a0d89660..9c3380695 100644
--- a/openslides/core/static/js/core/projector.js
+++ b/openslides/core/static/js/core/projector.js
@@ -157,17 +157,50 @@ angular.module('OpenSlidesApp.core.projector', ['OpenSlidesApp.core'])
         $scope.broadcast = 0;
 
         var setElements = function (projector) {
-            $scope.elements = [];
+            // Get all elements, that should be projected.
+            var newElements = [];
             _.forEach(slides.getElements(projector), function (element) {
                 if (!element.error) {
                     // Exclude the clock if it should be disabled.
                     if (Config.get('projector_enable_clock').value || element.name !== 'core/clock') {
-                        $scope.elements.push(element);
+                        newElements.push(element);
                     }
                 } else {
                     console.error("Error for slide " + element.name + ": " + element.error);
                 }
             });
+
+            // Now we have to align $scope.elements to newElements:
+            // We cannot just assign them, because the ng-repeat would reload every
+            // element. This should be prevented (see #3259). To change $scope.elements:
+            // 1) remove all elements from scope, that are not in newElements (compared by the uuid)
+            // 2) Every new element in newElements, that is not in $scope.elements, get inserted there.
+            // 3) If there is the same element in newElements and $scope.elements every changed property
+            //    is copied from the new element to the scope element.
+
+            $scope.elements = _.filter($scope.elements, function (element) {
+                return _.some(newElements, function (newElement) {
+                    return element.uuid === newElement.uuid;
+                });
+            });
+
+            _.forEach(newElements, function (newElement) {
+                var matchingElement = _.find($scope.elements, function (element) {
+                    return element.uuid === newElement.uuid;
+                });
+                if (matchingElement) {
+                    // copy all changed properties.
+                    _.forEach(newElement, function (value, key) {
+                        if (newElement.hasOwnProperty(key) && !key.startsWith('$')) {
+                            if (typeof matchingElement[key] === 'undefined' || matchingElement[key] !== value) {
+                                matchingElement[key] = value;
+                            }
+                        }
+                    });
+                } else {
+                    $scope.elements.push(newElement);
+                }
+            });
         };
 
         // This function scrolls the projector smoothly. It scrolls is steps calling each
diff --git a/openslides/mediafiles/static/js/mediafiles/projector.js b/openslides/mediafiles/static/js/mediafiles/projector.js
index fb9319bf1..175377ae8 100644
--- a/openslides/mediafiles/static/js/mediafiles/projector.js
+++ b/openslides/mediafiles/static/js/mediafiles/projector.js
@@ -18,11 +18,36 @@ angular.module('OpenSlidesApp.mediafiles.projector', [
 
 .controller('SlideMediafileCtrl', [
     '$scope',
+    '$timeout',
     'Mediafile',
-    function ($scope, Mediafile) {
+    function ($scope, $timeout, Mediafile) {
         // load mediafile object
         Mediafile.bindOne($scope.element.id, $scope, 'mediafile');
 
+        $scope.showPdf = true;
+
+        // Watch for page changes in the projector element. Adjust the page
+        // in the canvas scope, so the viewer can change the size automatically.
+        $scope.$watch(function () {
+            return $scope.element.page;
+        }, function () {
+            var canvasScope = angular.element('#pdf-canvas').scope();
+            if (canvasScope) {
+                canvasScope.pageNum = $scope.element.page;
+            }
+        });
+
+        // Watch for scale changes. If the scale is changed, reload the pdf
+        // viewer by just disable and re-enable it.
+        $scope.$watch(function () {
+            return $scope.element.scale;
+        }, function () {
+            $scope.showPdf = false;
+            $timeout(function () {
+                $scope.showPdf = true;
+            }, 1);
+        });
+
         // Allow the elements to render properly
         setTimeout(function() {
             if ($scope.mediafile) {
diff --git a/openslides/mediafiles/static/templates/mediafiles/slide_mediafile.html b/openslides/mediafiles/static/templates/mediafiles/slide_mediafile.html
index 19d5c182a..c28f06f48 100644
--- a/openslides/mediafiles/static/templates/mediafiles/slide_mediafile.html
+++ b/openslides/mediafiles/static/templates/mediafiles/slide_mediafile.html
@@ -1,7 +1,7 @@
 <div ng-controller="SlideMediafileCtrl" class="content" ng-class="{'fullscreen': element.fullscreen, 'video-container': element.is_video}">
     <!-- PDF -->
-    <ng-pdf ng-if="mediafile.is_pdf" template-url="/static/templates/mediafiles/slide_mediafile_partial.html"
-         ng-attr-scale="{{ element.scale }}"
+    <ng-pdf ng-if="mediafile.is_pdf && showPdf" template-url="/static/templates/mediafiles/slide_mediafile_partial.html"
+         scale="{{ element.scale }}"
          ng-attr-page="{{ element.page }}">
     </ng-pdf>