wc-wpo-wcpdf-invoice-minimum-order.php

<?php
define( 'INVOICE_GENERATION_MINIMUM_SUBTOTAL', 100 ); // se subtotale >= X€ IVA ESCUSA, allora genero la fattura

add_filter( 'wpo_wcpdf_document_is_allowed', function ( $allowed, $document ) {
	if ( ! $document->exists() && ! empty( $order = $document->order ) ) {
		if ( ! is_callable( array( $order, 'get_subtotal' ) ) ) {
			return false;
		}
		// check order total & setting
		$order_subtotal = $order->get_subtotal();
		if ( $order_subtotal < INVOICE_GENERATION_MINIMUM_SUBTOTAL ) {
			return false;
		} else {
			return $allowed;
		}
	} else {
		return $allowed;
	}
}, 10, 2 );