WordPress: Custom post type (my-document) for docs (PDFs, etc)

document.php

<?php
/*
Plugin Name: My Document Permalink
Description: Custom post type (my-document) for docs (PDFs, etc)
Version: 1.0
Author: Pete Nelson
*/

add_action('init', 'my_register_document_post_type');

function my_register_document_post_type()
{

	/*
	This plugin, in combination with a single-{post-type}.php template, allows you to create a permanent, friendly URL to
	a document, and my attaching new media to a post, keep that document updated.
	*/


	$type_name_s = 'Document';
	$type_name_p = 'Documents';

	$args = array(
		'public' => true, 
		'labels' => array(
				'name' => $type_name_p,
				'singular_name' => $type_name_s,
				'add_new_item' => 'Add New '. $type_name_s,
				'edit_item' => 'Edit ' . $type_name_s,
				'new_item' => 'New ' . $type_name_s,
				'new_item' => 'View ' . $type_name_s,
				'search_items' => 'Search ' . $type_name_p,
				'not_found' => 'No ' . $type_name_p . ' found',
				'not_found_in_trash' => 'No ' . $type_name_p . ' found in Trash'
			),
		'description' => 'Documents',
		'exclude_from_search' => true,
		'show_in_menu' => true,
		'capability_type' => 'post',
		'has_archive' => true,
		'rewrite' => array(
			'slug' => 'document',
			)

		);


	register_post_type('my-document', $args);

}

single-my-document.php

<?php 

// gets the most recent attachment for this post
$attachments = get_children(array( 
	'post_parent' => get_the_id(),
	'post_type'   => 'attachment', 
	'numberposts' => 1,
	'post_status' => 'any',
	'orderby'     => 'post_date',
	'order'       => 'DESC',
	)
);


if ($attachments && count($attachments) > 0) 
{

	$attachment = array_values($attachments);
	$attachment = $attachment[0];
	
	$file = get_attached_file($attachment->ID);


	// this will output the file directly to the browser, but you may want to redirect 
	// to the attachment's URL instead

	$filesize = filesize($file);

	header('Content-Type: ' . $attachment->post_mime_type);
	header('Content-Length: ' . $filesize);
	header('Content-Disposition: inline; filename=' . basename($file));

	ob_clean();
	flush();
	readfile($file);

}
else {
	header("HTTP/1.0 404 Not Found");
}

exit;