get a list of pdf files used for a certain post category

gistfile1.txt

<?php 
include "wp-load.php";
?>


<?php query_posts('category_name={{yourcategoryname}}&posts_per_page=-1'); ?>
    <?php while (have_posts()) : the_post(); ?>
        <?php
            $args = array(
                'order'          => 'ASC',
                'post_type'      => 'attachment',
                'post_parent'    => $post->ID,
                'date_query'     => array(
                    'before' => array(
                        'year'  => 2019,
                        'month' => 1,
                        'day'   => 1,
                    ),
                ),                            
                'post_mime_type' => 'application/pdf',
                //'post_status'    => null,
                'numberposts'    => -1,
                );
                $attachments = get_posts($args);
                if ($attachments) {
                    foreach ($attachments as $attachment) {
                        echo wp_get_attachment_url($attachment->ID);
                        echo "<br>";
                        }
                    }
                    ?>
    <?php endwhile;?>