Attach PDF files to post with custom metabox file selection

add_action("admin_init", "pdf_init");
add_action('save_post', 'save_pdf_link');
function pdf_init(){
	add_meta_box("my-pdf", "PDF Document", "pdf_link", "post", "normal", "low");
	}
function pdf_link(){
	global $post;
	$custom  = get_post_custom($post->ID);
	$link    = $custom["link"][0];
	$count   = 0;
	echo '<div class="link_header">';
	$query_pdf_args = array(
		'post_type' => 'attachment',
		'post_mime_type' =>'application/pdf',
		'post_status' => 'inherit',
		'posts_per_page' => -1,
		);
	$query_pdf = new WP_Query( $query_pdf_args );
	$pdf = array();
	echo '<select name="link">';
	echo '<option class="pdf_select">SELECT pdf FILE</option>';
	foreach ( $query_pdf->posts as $file) {
	   if($link == $pdf[]= $file->guid){
	      echo '<option value="'.$pdf[]= $file->guid.'" selected="true">'.$pdf[]= $file->guid.'</option>';
		 }else{
	      echo '<option value="'.$pdf[]= $file->guid.'">'.$pdf[]= $file->guid.'</option>';
		 }
		$count++;
	}
	echo '</select><br /></div>';
	echo '<p>Selecting a pdf file from the above list to attach to this post.</p>';
	echo '<div class="pdf_count"><span>Files:</span> <b>'.$count.'</b></div>';
}
function save_pdf_link(){
	global $post;
	if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE){ return $post->ID; }
	update_post_meta($post->ID, "link", $_POST["link"]);
}
add_action( 'admin_head', 'pdf_css' );
function pdf_css() {
	echo '<style type="text/css">
	.pdf_select{
		font-weight:bold;
		background:#e5e5e5;
		}
	.pdf_count{
		font-size:9px;
		color:#0066ff;
		text-transform:uppercase;
		background:#f3f3f3;
		border-top:solid 1px #e5e5e5;
		padding:6px 6px 6px 12px;
		margin:0px -6px -8px -6px;
		-moz-border-radius:0px 0px 6px 6px;
		-webkit-border-radius:0px 0px 6px 6px;
		border-radius:0px 0px 6px 6px;
		}
	.pdf_count span{color:#666;}
		</style>';
}
function pdf_file_url(){
	global $wp_query;
	$custom = get_post_custom($wp_query->post->ID);
	echo $custom['link'][0];
}

<? pdf_file_url(); ?>

<a href="<? pdf_file_url(); ?>">My PDF File</a>