Add download categories from Easy Digital Downloads to the post_class

gistfile1.php

<?php
function my_child_theme_post_classes( $classes ) {
	// get the terms from our 'download_category' taxonomy
	$terms = get_the_terms( get_the_ID(), 'download_category' );

	if ( $terms && ! is_wp_error( $terms ) ) {
		// add each term slug to our classes array
		foreach ( $terms as $term ) {
			$classes[] = $term->slug;
		}
	} 
	
	return $classes;
}
add_filter( 'post_class', 'my_child_theme_post_classes' );