Extend an Order Form for WooCommerce form with WordPress hooks, instead of hacking templates. Requires version 1.4.0 or higher. Save this file as a simple plugin in the WordPress plugins folder. http://orderform-woo.webaware.net.au/

orderform-woo-extend-form.php

<?php
/*
Plugin Name: Order Form for WooCommerce extend form
Plugin URI: https://gist.github.com/webaware/1fe598e60f9ad9a912ee
Description: example form extras using hooks
Author: WebAware
Author URI: http://webaware.com.au/
*/


/**
* show the submit/clear buttons at the top of the form too
*/
add_action('orderform_woocommerce_form_start', function($attrs) {
    ?>

    <p style="clear:both">
        <button type="submit" class="single_add_to_cart_button button alt"><?php echo esc_html($attrs['submittitle']); ?></button>
        <button style="display:none" class="single_add_to_cart_button button alt" name="clear-form"><?php echo esc_html($attrs['cleartitle']); ?></button>
    </p>

    <?php
});


/**
* insert a column before Price -- table header
* change the text to the column heading you want
*/
add_action('orderform_woocommerce_before_order_price_head', function($attrs) {
    ?>

    <th class="your-custom-column-class">Custom</th>

    <?php
});


/**
* insert a column before Price -- table footer
* this shows just a blank cell, but you can put whatever you want there
*/
add_action('orderform_woocommerce_before_order_price_foot', function($attrs) {
    ?>

    <td class="your-custom-column-class">&nbsp;</td>

    <?php
});


/**
* insert a column before Price -- table body
* e.g. get other WooCommerce product data and show it here
*/
add_action('orderform_woocommerce_before_order_price', function($product, $attrs) {
    $stock = $product->get_total_stock();
    ?>

    <td class="your-custom-column-class"><?php echo number_format($stock); ?></td>

    <?php
}, 10, 2);