pdf파일 다운로드방법ㅠ

<?				set_session('ss_view_'.$bo_table.'_'.$list[$i][wr_id], TRUE);				$sql = " select * from $g5[board_file_table] where bo_table = '". $bo_table. "' and wr_id = '". $list[$i][wr_id] ."' order by bf_no ";				$result = sql_query($sql);				while ($row = sql_fetch_array($result))				{					$down_link = "download.php?bo_table={$bo_table}&wr_id={$list[$i][wr_id]}&no={$row[bf_no]}";					$file_source = addslashes($row[bf_source]);					$file_type = preg_replace('/^.*\.([^.]+)$/D', '$1', $file_source);					$file_size = get_filesize($row[bf_filesize]); 					// file_type에 다르게 아이콘 변경					switch ($file_type){						case 'docx':							$img_src = $board_skin_url.'/img/icon_word.gif';							$file_alt = "워드";							$file_title = "DOC";							break;						case 'hwp':							$img_src = $board_skin_url.'/img/icon_hwp.gif';							$file_alt = "한글";							$file_title = "HWP";							break;						case 'pdf':							$img_src = $board_skin_url.'/img/icon_pdf.png';							$file_alt = "PDF";							$file_title = "PDF";							break;						default:							$img_src= 'Null';					} 					if(!in_array($file_type, array('jpg', 'jpeg', 'gif', 'bmp', 'png'))){	//이미지는 제외						echo "<a href=\"".$down_link."\" title=\"".$file_source."\" class='btn_download'>";						echo "<img src='". $img_src."' alt=\"".$file_alt." 아이콘\">";						echo "<span>".$file_title." 다운로드</span>";						echo "</a>";					}				}			 ?>