diff --git a/public/main/inc/lib/certificate.lib.php b/public/main/inc/lib/certificate.lib.php
index 4a0502d0604..172b3ef3878 100644
--- a/public/main/inc/lib/certificate.lib.php
+++ b/public/main/inc/lib/certificate.lib.php
@@ -2,7 +2,6 @@
 
 /* For licensing terms, see /license.txt */
 
-use Chamilo\CoreBundle\Component\Mpdf\SafeMpdfHttpClient;
 use Chamilo\CoreBundle\Entity\GradebookCategory;
 use Chamilo\CoreBundle\Entity\PersonalFile;
 use Chamilo\CoreBundle\Entity\ResourceFile;
@@ -1007,32 +1006,7 @@ public function generateCustomCertificate(string $fileName = ''): string
     public function generatePdfFromCustomCertificate(): void
     {
         $orientation = api_get_setting('certificate.certificate_pdf_orientation');
-
-        $pdfOrientation = 'landscape';
-        if (!empty($orientation)) {
-            $pdfOrientation = $orientation;
-        }
-
-        $pageFormat = 'landscape' === $pdfOrientation ? 'A4-L' : 'A4';
-
-        // Instanciate mPDF directly to avoid blank pages generated by the default
-        // PDF class: format_pdf() sets mirrorMargins=1 (book layout) and the
-        // constructor hard-codes margin_header=8 / margin_footer=8 even when
-        // headers and footers are empty, which causes mPDF to insert blank
-        // odd/even pages around the single certificate page.
-        $mpdf = new \Mpdf\Mpdf([
-            'tempDir'        => Container::getCacheDir(),
-            'mode'           => 'utf-8',
-            'format'         => $pageFormat,
-            'orientation'    => $pdfOrientation,
-            'margin_left'    => 0,
-            'margin_right'   => 0,
-            'margin_top'     => 0,
-            'margin_bottom'  => 0,
-            'margin_header'  => 0,
-            'margin_footer'  => 0,
-        ], SafeMpdfHttpClient::container());
-        $mpdf->mirrorMargins = 0;
+        $pdfOrientation = !empty($orientation) ? $orientation : 'landscape';
 
         // Safety: ensure HTML content is present; fetch from Resource if needed.
         if (empty($this->certificate_data['file_content'])) {
@@ -1048,11 +1022,14 @@ public function generatePdfFromCustomCertificate(): void
             }
         }
 
-        @$mpdf->WriteHTML((string) $this->certificate_data['file_content']);
-
-        $pdfName = api_replace_dangerous_char(get_lang('Certificates'));
-        $mpdf->Output($pdfName.'.pdf', \Mpdf\Output\Destination::DOWNLOAD);
-        exit;
+        // Single-page render with SSRF-guarded mPDF lives in the PDF class; it
+        // skips format_pdf()'s book layout to avoid blank pages around the
+        // single certificate page.
+        PDF::singlePageHtmlToPdfDownload(
+            (string) $this->certificate_data['file_content'],
+            get_lang('Certificates'),
+            $pdfOrientation
+        );
     }
 
     /**
diff --git a/public/main/inc/lib/pdf.lib.php b/public/main/inc/lib/pdf.lib.php
index ae784246c10..d150015543c 100644
--- a/public/main/inc/lib/pdf.lib.php
+++ b/public/main/inc/lib/pdf.lib.php
@@ -52,6 +52,7 @@ public function __construct(
         $params['right'] = $params['right'] ?? 15;
         $params['top'] = $params['top'] ?? 30;
         $params['bottom'] = $params['bottom'] ?? 30;
+        $params['margin_header'] = $params['margin_header'] ?? 8;
         $params['margin_footer'] = $params['margin_footer'] ?? 8;
 
         $this->params['filename'] = $params['filename'] ?? api_get_local_time();
@@ -77,8 +78,8 @@ public function __construct(
             'margin_right' => $params['right'],
             'margin_top' => $params['top'],
             'margin_bottom' => $params['bottom'],
-            'margin_header' => 8,
-            'margin_footer' => 8,
+            'margin_header' => $params['margin_header'],
+            'margin_footer' => $params['margin_footer'],
         ];
 
         // Default value is 96 set in the mpdf library file config.php
@@ -538,6 +539,44 @@ public function content_to_pdf(
         return $output_file;
     }
 
+    /**
+     * Renders single-page HTML (e.g. a certificate) to a downloadable PDF.
+     *
+     * Reuses the SSRF-guarded mPDF instance built by the constructor, with all
+     * margins set to 0 and without calling format_pdf(): this deliberately
+     * skips the book-layout decoration (mirrorMargins, header/footer margins)
+     * that would otherwise insert blank pages around a single-page document.
+     *
+     * @param string $html        HTML content to render
+     * @param string $fileName    Output file name (without extension)
+     * @param string $orientation 'landscape' or 'portrait'
+     *
+     * @throws MpdfException
+     */
+    public static function singlePageHtmlToPdfDownload(
+        string $html,
+        string $fileName,
+        string $orientation = 'landscape'
+    ): void {
+        $pageFormat = 'landscape' === $orientation ? 'A4-L' : 'A4';
+        $mpdfOrientation = 'landscape' === $orientation ? 'L' : 'P';
+
+        $pdf = new self($pageFormat, $mpdfOrientation, [
+            'left'          => 0,
+            'right'         => 0,
+            'top'           => 0,
+            'bottom'        => 0,
+            'margin_header' => 0,
+            'margin_footer' => 0,
+        ]);
+        $pdf->pdf->mirrorMargins = 0;
+
+        @$pdf->pdf->WriteHTML($html);
+
+        $pdf->pdf->Output(api_replace_dangerous_char($fileName).'.pdf', Destination::DOWNLOAD);
+        exit;
+    }
+
     /**
      * Gets the watermark from the platform or a course.
      *