Enqueue custom print.css file for Paid Memberships Pro.

enqueue-print-css-pmpro-theme-or-plugin.php

<?php
/**
 * If anyone created a custom print.css file, add this code to a custom plugin to re-enqueue it in your theme or template directory.
 */
function my_enqueue_print_style() {
	if ( file_exists( get_stylesheet_directory() . '/paid-memberships-pro/css/print.css' ) ) {
		$print_css = get_stylesheet_directory_uri() . '/paid-memberships-pro/css/print.css';
	} elseif ( file_exists( get_template_directory() . '/paid-memberships-pro/print.css' ) ) {
		$print_css = get_template_directory_uri() . '/paid-memberships-pro/print.css';
	} else {
		return;
	}

	wp_enqueue_style( 'pmpro-print', $print_css, array(), '1.0', 'print' );
}
add_action( 'wp_enqueue_scripts', 'my_enqueue_print_style' );