title: Add a pdf attachment to WooCommerce completed order email notification
body: <p>Found this code on another thread but can't make it work.
  PDF uploaded to wp-content/child-theme/.</p>
  
  <p>Goal is to attach the pdf to the completed order emails that woocommerce will send out.</p>
  
  <p>Not sure if <code>customer_completed_order</code> is correct?</p>
  
  <pre><code>add_filter( 'woocommerce_email_attachments', 'attach_terms_conditions_pdf_to_email', 10, 3 );
  function attach_terms_conditions_pdf_to_email ( $attachments , $email_id, $email_object ) {
      // Avoiding errors and problems
      if ( ! is_a( $order, 'WC_Order' ) || ! isset( $email_id ) ) {
          return $attachments;
      }
  
  
      if( $email_id === 'customer_completed_order' ){
  
          $your_pdf_path = get_stylesheet_directory() . '/Q-0319B.pdf';
          $attachments[] = $your_pdf_path;
      }
  
      return $attachments;
  }
  </code></pre>