$dir_jpg = "../wp-content/uploads/newspaper/jpg/";
    $dir_pdf = "../wp-content/uploads/newspaper/pdf/";

        $images = glob($dir_jpg."*.*");
        $pdfs = glob($dir_pdf."*.*");

        $array = array_combine($images, $pdfs);

        foreach($array as $image => $pdf){
          echo '<ul>';
            echo '<li>';
              echo '<a href="'.$pdf.'" target="_blank"><img src="'.$image.'" height="100" width="100" /></a>';
            echo '</li>';
          echo '</ul>';
        }