Das Format kannst du direkt in den Dokumenten-Templates ändern.
{% sw_extends '@Framework/documents/invoice.html.twig' %}
{% block document_side_info_order_date %}
<tr>
<td>
{{ 'document.orderDate'|trans({'%orderDate%': order.orderDateTime|format_date(pattern="dd.MM.Y", locale=locale)})|sw_sanitize }}
</td>
</tr>
{% endblock %}
{% block document_side_info_date %}
<tr>
<td>
{{ 'document.date'|trans({'%date%': config.documentDate|format_date(pattern="dd.MM.Y", locale=locale)})|sw_sanitize }}
</td>
</tr>
{% endblock %}