<?php
add_filter( 'woo_vou_pdf_template_replace_shortcodes', 'woo_vou_pdf_change_booking_date_shortcodes', 999, 6 );
function woo_vou_pdf_change_booking_date_shortcodes( $woo_vou_details, $orderid, $item_key, $items, $voucodes, $productid ){
  // code to change booking date shortcode date format on voucher pdf
  if( isset( $woo_vou_details['booking_date'] ) && !empty( $woo_vou_details['booking_date'] ) ){
			$woo_vou_details['booking_date'] = date( 'Y-M-D', strtotime( $woo_vou_details['booking_date'] ) );
	}

		return $woo_vou_details;
}