Automatically convert permalinks to PDFs in search results to the PDF itself, not the Attachment page

functions.php

<?php

// Automatically convert permalinks to PDFs in search results to the PDF itself, not the Attachment page
add_filter( 'the_permalink', function( $permalink ) {
	global $post;
	
	if ( is_search() && 'application/pdf' == get_post_mime_type( $post->ID ) ) {
		// if the result is a PDF, link directly to the file not the attachment page
		$permalink = wp_get_attachment_url( $post->ID );
	}

	return $permalink;
} );