gistfile1.phtml

<?php
/*
 * Plugin Name: EDD Redirect to Next Product on Add to Cart
 * Description: Automatically redirects the customer to the next product after they have added an item to the cart
 * Author: Pippin Williamson
 * Version: 0.1
 */

function pw_edd_redirect_to_next_scripts( $download_id = 0 ) {

	global $post;

	$post = get_post( $download_id );

	setup_postdata( $post );

	$next = get_adjacent_post();

	wp_reset_postdata();

	if( ! $next ) {
		return false; // No additional products
	}

?>
	<script>
	jQuery(document).ready(function($) {
		$('body').on('edd_cart_item_added', function( response ) {
			window.location = "<?php echo get_permalink( $next->ID ); ?>";
		});
	});
	</script>
<?php
}
add_action( 'edd_after_download_content', 'pw_edd_redirect_to_next_scripts' );