diff --git a/htdocs/core/actions_massactions.inc.php b/htdocs/core/actions_massactions.inc.php
index 74badc6daae..58e47a29ec8 100644
--- a/htdocs/core/actions_massactions.inc.php
+++ b/htdocs/core/actions_massactions.inc.php
@@ -406,60 +406,105 @@ if (! $error && $massaction == "builddoc" && $permtoread && ! GETPOST('button_se
         $outputlangs->setDefaultLang($newlang);
     }
 
-    // Create empty PDF
-    $pdf=pdf_getInstance();
-    if (class_exists('TCPDF'))
-    {
-        $pdf->setPrintHeader(false);
-        $pdf->setPrintFooter(false);
+    if(!empty($conf->global->USE_PDFTK_FOR_PDF_CONCAT)) {
+    	// Create output dir if not exists
+	dol_mkdir($diroutputmassaction);
+
+	// Defined name of merged file
+	$filename=strtolower(dol_sanitizeFileName($langs->transnoentities($objectlabel)));
+	$filename=preg_replace('/\s/','_',$filename);
+
+	// Save merged file
+	if ($filter=='paye:0')
+	{
+	if ($option=='late') $filename.='_'.strtolower(dol_sanitizeFileName($langs->transnoentities("Unpaid"))).'_'.strtolower(dol_sanitizeFileName($langs->transnoentities("Late")));
+	else $filename.='_'.strtolower(dol_sanitizeFileName($langs->transnoentities("Unpaid")));
+	}
+	if ($year) $filename.='_'.$year;
+	if ($month) $filename.='_'.$month;
+
+    	if (count($files)>0)
+    	{
+    	
+    		$now=dol_now();
+    		$file=$diroutputmassaction.'/'.$filename.'_'.dol_print_date($now,'dayhourlog').'.pdf';
+    		
+    		$input_files = '';
+    		foreach($files as $f) {
+    			$input_files.=' '.escapeshellarg($f);
+    		}
+    		
+    		$cmd = 'pdftk '.$input_files.' cat output '.escapeshellarg($file);
+    		exec($cmd);
+    		
+    		if (! empty($conf->global->MAIN_UMASK))
+    			@chmod($file, octdec($conf->global->MAIN_UMASK));
+    			
+    			$langs->load("exports");
+    			setEventMessages($langs->trans('FileSuccessfullyBuilt',$filename.'_'.dol_print_date($now,'dayhourlog')), null, 'mesgs');
+    	}
+    	else
+    	{
+    		setEventMessages($langs->trans('NoPDFAvailableForDocGenAmongChecked'), null, 'errors');
+    	}
+    	
     }
-    $pdf->SetFont(pdf_getPDFFont($outputlangs));
+    else {
+	    // Create empty PDF
+	    $pdf=pdf_getInstance();
+	    if (class_exists('TCPDF'))
+	    {
+		$pdf->setPrintHeader(false);
+		$pdf->setPrintFooter(false);
+	    }
+	    $pdf->SetFont(pdf_getPDFFont($outputlangs));
 
-    if (! empty($conf->global->MAIN_DISABLE_PDF_COMPRESSION)) $pdf->SetCompression(false);
+	    if (! empty($conf->global->MAIN_DISABLE_PDF_COMPRESSION)) $pdf->SetCompression(false);
 
-    // Add all others
-    foreach($files as $file)
-    {
-        // Charge un document PDF depuis un fichier.
-        $pagecount = $pdf->setSourceFile($file);
-        for ($i = 1; $i <= $pagecount; $i++)
-        {
-            $tplidx = $pdf->importPage($i);
-            $s = $pdf->getTemplatesize($tplidx);
-            $pdf->AddPage($s['h'] > $s['w'] ? 'P' : 'L');
-            $pdf->useTemplate($tplidx);
-        }
-    }
+	    // Add all others
+	    foreach($files as $file)
+	    {
+		// Charge un document PDF depuis un fichier.
+		$pagecount = $pdf->setSourceFile($file);
+		for ($i = 1; $i <= $pagecount; $i++)
+		{
+		    $tplidx = $pdf->importPage($i);
+		    $s = $pdf->getTemplatesize($tplidx);
+		    $pdf->AddPage($s['h'] > $s['w'] ? 'P' : 'L');
+		    $pdf->useTemplate($tplidx);
+		}
+	    }
 
-    // Create output dir if not exists
-    dol_mkdir($diroutputmassaction);
+	    // Create output dir if not exists
+	    dol_mkdir($diroutputmassaction);
 
-    // Defined name of merged file
-    $filename=strtolower(dol_sanitizeFileName($langs->transnoentities($objectlabel)));
-    $filename=preg_replace('/\s/','_',$filename);
-    
-    // Save merged file
-    if ($filter=='paye:0')
-    {
-        if ($option=='late') $filename.='_'.strtolower(dol_sanitizeFileName($langs->transnoentities("Unpaid"))).'_'.strtolower(dol_sanitizeFileName($langs->transnoentities("Late")));
-        else $filename.='_'.strtolower(dol_sanitizeFileName($langs->transnoentities("Unpaid")));
-    }
-    if ($year) $filename.='_'.$year;
-    if ($month) $filename.='_'.$month;
-    if ($pagecount)
-    {
-        $now=dol_now();
-        $file=$diroutputmassaction.'/'.$filename.'_'.dol_print_date($now,'dayhourlog').'.pdf';
-        $pdf->Output($file,'F');
-        if (! empty($conf->global->MAIN_UMASK))
-            @chmod($file, octdec($conf->global->MAIN_UMASK));
+	    // Defined name of merged file
+	    $filename=strtolower(dol_sanitizeFileName($langs->transnoentities($objectlabel)));
+	    $filename=preg_replace('/\s/','_',$filename);
+	    
+	    // Save merged file
+	    if ($filter=='paye:0')
+	    {
+		if ($option=='late') $filename.='_'.strtolower(dol_sanitizeFileName($langs->transnoentities("Unpaid"))).'_'.strtolower(dol_sanitizeFileName($langs->transnoentities("Late")));
+		else $filename.='_'.strtolower(dol_sanitizeFileName($langs->transnoentities("Unpaid")));
+	    }
+	    if ($year) $filename.='_'.$year;
+	    if ($month) $filename.='_'.$month;
+	    if ($pagecount)
+	    {
+		$now=dol_now();
+		$file=$diroutputmassaction.'/'.$filename.'_'.dol_print_date($now,'dayhourlog').'.pdf';
+		$pdf->Output($file,'F');
+		if (! empty($conf->global->MAIN_UMASK))
+		    @chmod($file, octdec($conf->global->MAIN_UMASK));
 
-            $langs->load("exports");
-            setEventMessages($langs->trans('FileSuccessfullyBuilt',$filename.'_'.dol_print_date($now,'dayhourlog')), null, 'mesgs');
-    }
-    else
-    {
-        setEventMessages($langs->trans('NoPDFAvailableForDocGenAmongChecked'), null, 'errors');
+		    $langs->load("exports");
+		    setEventMessages($langs->trans('FileSuccessfullyBuilt',$filename.'_'.dol_print_date($now,'dayhourlog')), null, 'mesgs');
+	    }
+	    else
+	    {
+		setEventMessages($langs->trans('NoPDFAvailableForDocGenAmongChecked'), null, 'errors');
+	    }
     }
 }