By default, the built-in WordPress media manager allows you to filter media by three types: images, audio and video. But if you work a lot with .pdf files, you may need to add an option to filter .pdf files from the media manager. Here is a simple code snippet to do it.

Paste this code into your functions.php file. Save the file, and you’re done.

 function modify_post_mime_types( $post_mime_types ) {  	// select the mime type, here: 'application/pdf' 	// then we define an array with the label values  	$post_mime_types['application/pdf'] = array( __( 'PDFs' ), __( 'Manage PDFs' ), _n_noop( 'PDF <span class="count">(%s)</span>', 'PDFs <span class="count">(%s)</span>' ) );  	// then we return the $post_mime_types variable 	return $post_mime_types;  }  // Add Filter Hook add_filter( 'post_mime_types', 'modify_post_mime_types' ); 

Note that this code snippet can be used for other file types as well as .swf, .avi, .mov, etc.

Thanks to WP Tuts for the nice code snippets!