I am trying to call an ACF value from a WooCommerce product, so I can display it in an invoice, but having issues on grabbing the specific information for that. I’ve added a screenshot of the ‘Internal ID’ which is the ACF field and value.

ACF Field Value in a product (setting example):

I need to add that to the following:

<?php do_action( 'wpo_wcpdf_before_order_details', $this->get_type(), $this->order ); ?>

<table class="order-details">
    <thead>
        <tr>
            <th class="product"><?php _e( 'Product Name', 'woocommerce-pdf-invoices-packing-slips' ); ?></th>
            <th class="reference"><?php _e( 'Product Reference', 'woocommerce-pdf-invoices-packing-slips' ); ?></th>
            <th class="pick_quantity"><?php _e( 'Pick Qty', 'woocommerce-pdf-invoices-packing-slips' ); ?></th>
            <th class="price"><?php _e( 'Price ex.VAT', 'woocommerce-pdf-invoices-packing-slips' ); ?></th>
            <th class="vat"><?php _e( 'VAT', 'woocommerce-pdf-invoices-packing-slips' ); ?></th>
            <th class="price"><?php _e( 'Price inc.VAT', 'woocommerce-pdf-invoices-packing-slips' ); ?></th>
        </tr>
    </thead>
    <tbody>
        <?php foreach ( $this->get_order_items() as $item_id => $item ) : ?>
            <tr class="<?php echo apply_filters( 'wpo_wcpdf_item_row_class', 'item-'.$item_id, $this->get_type(), $this->order, $item_id ); ?>">
                <td class="product">
                    <?php $description_label = __( 'Description', 'woocommerce-pdf-invoices-packing-slips' ); // registering alternate label translation ?>
                    <span class="item-name"><?php echo $item['name']; ?></span>
                    <?php do_action( 'wpo_wcpdf_after_item_meta', $this->get_type(), $item, $this->order  ); ?>
                </td>
                <td class="reference">
                    
                        <?php if ( ! empty( $item['sku'] ) ) : ?><dt class="sku"><dd class="sku"><?php echo $item['sku']; ?></dd><?php endif; ?>
                        <?php echo $item['thumbnail']?> 
                </td>
                <td class="pick_quantity"><?php 
        echo $item['quantity'];         
                    ?></td>
                <td class="price"><?php echo $item['line_total']; ?></td>
                <td class="vat"><?php echo $item['line_tax']; ?></td>
                <td class="price"><?php echo $item['order_price']; ?></td>
            </tr>
        <?php endforeach; ?>
    </tbody>
    <tfoot>

Ideally I would like to change out the line:

<?php if ( ! empty( $item['sku'] ) ) : ?><dt class="sku"><dd class="sku"><?php echo $item['sku']; ?></dd><?php endif; ?>

for the ‘Internal ID’ from ACF.

If anyone could help that would be great, as I’m a complete novice with this.