diff --git a/.env.dist b/.env.dist
index b76e558a27..d25e1dbd1f 100644
--- a/.env.dist
+++ b/.env.dist
@@ -90,3 +90,6 @@ MYSQL_ALLOW_EMPTY_PASSWORD='yes'
 
 # This makes debugging with XDebug and PHPStorm easier
 PHP_IDE_CONFIG=serverName=gewis.nl
+
+# This is a tag for the course documents watermarking
+WATERMARK_TAG=test123
diff --git a/config/autoload/local.development.php.dist b/config/autoload/local.development.php.dist
index 4fb718a77b..8206c1cf2d 100644
--- a/config/autoload/local.development.php.dist
+++ b/config/autoload/local.development.php.dist
@@ -79,6 +79,13 @@ return [
         'supremum_api_key' => getenv('DOCKER_SUPREMUM_API_KEY'),
     ],
 
+    /**
+     * The config for watermarking
+     */
+    'watermark' => [
+        'tag' => getenv('WATERMARK_TAG'),
+    ],
+
     /*
      * Path to folder in local filesystem available for browsing
      */
diff --git a/config/autoload/local.production.php.dist b/config/autoload/local.production.php.dist
index 5e538f2398..13ee6e7c9e 100644
--- a/config/autoload/local.production.php.dist
+++ b/config/autoload/local.production.php.dist
@@ -79,6 +79,13 @@ return [
         'supremum_api_key' => getenv('DOCKER_SUPREMUM_API_KEY'),
     ],
 
+    /**
+     * The config for watermarking
+     */
+    'watermark' => [
+        'tag' => getenv('WATERMARK_TAG'),
+    ],
+
     /*
      * Path to folder in local filesystem available for browsing
      */
diff --git a/module/Application/src/Module.php b/module/Application/src/Module.php
index ae3f7ba757..a239ec9e36 100644
--- a/module/Application/src/Module.php
+++ b/module/Application/src/Module.php
@@ -168,8 +168,9 @@ public function getServiceConfig(): array
                     /** @var AuthenticationService<UserSession, UserAdapter> $authService */
                     $authService = $container->get('user_auth_user_service');
                     $remoteAddress = $container->get('user_remoteaddress');
+                    $watermarkConfig = $container->get('config')['watermark'];
 
-                    return new WatermarkService($authService, $remoteAddress);
+                    return new WatermarkService($authService, $remoteAddress, $watermarkConfig);
                 },
                 'application_get_languages' => static function () {
                     return ['nl', 'en'];
diff --git a/module/Application/src/Service/WatermarkService.php b/module/Application/src/Service/WatermarkService.php
index 2973c7573f..a71271ca45 100644
--- a/module/Application/src/Service/WatermarkService.php
+++ b/module/Application/src/Service/WatermarkService.php
@@ -29,13 +29,16 @@ class WatermarkService
     private const FONT_SIZE_DIAGONAL = 32;
     private const FONT_SIZE_HORIZONTAL = 8;
     private const FONT = 'freesansb';
+    private const TAG_FONT = 'times';
 
     /**
      * @psalm-param TUserAuth $authService
+     * @psalm-param array{tag: string} $watermarkConfig
      */
     public function __construct(
         private readonly AuthenticationService $authService,
         private readonly string $remoteAddress,
+        private readonly array $watermarkConfig,
     ) {
     }
 
@@ -70,8 +73,8 @@ public function watermarkPdf(
             // Do the actual watermarking.
             $pdf->setFont(self::FONT, '', self::FONT_SIZE_DIAGONAL);
             $pdf->setTextColor(212, 0, 0);
-            // Set alpha to 50% for the diagonal watermark, the horizontal watermark will have a higher alpha.
-            $pdf->setAlpha(0.5);
+            // Set alpha to 35% for the diagonal watermark, the horizontal watermark will have a higher alpha.
+            $pdf->setAlpha(0.35);
 
             // Determine the position of the diagonal watermark, it should be (almost) centred on the page.
             $width = $pdf->getPageWidth();
@@ -144,7 +147,41 @@ public function watermarkPdf(
             ),
         );
 
-        return $tempFlatFile;
+        // Construct final PDF.
+        $taggedPdf = new Fpdi();
+        $taggedPdf->setTitle($fileName);
+        $pages = $taggedPdf->setSourceFile($tempFlatFile);
+
+        $tag = $this->watermarkConfig['tag'];
+
+        // We have to copy all pages to this new PDF.
+        for ($page = 1; $page <= $pages; $page++) {
+            $templateIndex = $taggedPdf->importPage($page);
+            $templateSpecs = $taggedPdf->getTemplateSize($templateIndex);
+            $taggedPdf->setPrintHeader(false);
+            $taggedPdf->setPrintFooter(false);
+            $taggedPdf->AddPage($templateSpecs['orientation']);
+            $taggedPdf->useTemplate($templateIndex, 0, 0, $templateSpecs['width'], $templateSpecs['height'], true);
+
+            // Early exit if we are not working on the first page.
+            if (1 !== $page) {
+                continue;
+            }
+
+            // Write the tag on the first page in the top left corner.
+            $taggedPdf->setFont(self::TAG_FONT, '', 6);
+            $taggedPdf->setTextColor(255, 255, 255);
+
+            $taggedPdf->StartTransform();
+            $taggedPdf->setXY(0, 0);
+            $taggedPdf->Write(0, $tag);
+            $taggedPdf->StopTransform();
+        }
+
+        $tempTaggedFile = $tempName . '-tagged.pdf';
+        $taggedPdf->Output($tempTaggedFile, 'F');
+
+        return $tempTaggedFile;
     }
 
     /**