diff --git a/src/Plugin/EntityPrint/PrintEngine/DomPdf.php b/src/Plugin/EntityPrint/PrintEngine/DomPdf.php
index 3c4cd14..9c16283 100644
--- a/src/Plugin/EntityPrint/PrintEngine/DomPdf.php
+++ b/src/Plugin/EntityPrint/PrintEngine/DomPdf.php
@@ -39,6 +39,13 @@ class DomPdf extends PdfEngineBase implements ContainerFactoryPluginInterface {
   protected $html = '';
 
   /**
+   * Keep track of whether we've rendered or not.
+   *
+   * @var bool
+   */
+  protected $hasRendered;
+
+  /**
    * {@inheritdoc}
    */
   public function __construct(array $configuration, $plugin_id, $plugin_definition, ExportTypeInterface $export_type, Request $request) {
@@ -143,7 +150,7 @@ class DomPdf extends PdfEngineBase implements ContainerFactoryPluginInterface {
    * {@inheritdoc}
    */
   public function send($filename, $force_download = TRUE) {
-    $this->dompdf->render();
+    $this->doRender();
 
     // Dompdf doesn't have a return value for send so just check the error
     // global it provides.
@@ -164,12 +171,21 @@ class DomPdf extends PdfEngineBase implements ContainerFactoryPluginInterface {
    * {@inheritdoc}
    */
   public function getBlob() {
-    $this->dompdf->render();
-
+    $this->doRender();
     return $this->dompdf->output();
   }
 
   /**
+   * Tell Dompdf to render the HTML into a PDF.
+   */
+  protected function doRender() {
+    if (!$this->hasRendered) {
+      $this->dompdf->render();
+      $this->hasRendered = TRUE;
+    }
+  }
+
+  /**
    * {@inheritdoc}
    */
   protected function getError() {
diff --git a/src/Plugin/EntityPrint/PrintEngine/PhpWkhtmlToPdf.php b/src/Plugin/EntityPrint/PrintEngine/PhpWkhtmlToPdf.php
index 8c15c83..e747b6b 100644
--- a/src/Plugin/EntityPrint/PrintEngine/PhpWkhtmlToPdf.php
+++ b/src/Plugin/EntityPrint/PrintEngine/PhpWkhtmlToPdf.php
@@ -99,7 +99,7 @@ class PhpWkhtmlToPdf extends PdfEngineBase implements AlignableHeaderFooterInter
    * {@inheritdoc}
    */
   public function getBlob() {
-    $this->pdf->toString();
+    return $this->pdf->toString();
   }
 
   /**