whatsapp_web_groups/cutom_report_invoice/views/account_move_views.xml

<?xml version='1.0' encoding='utf-8'?>
<odoo>
    <template id="custom_rate_report_invoice_document" inherit_id="account.report_invoice_document">
        <xpath expr="//div[@name='reference']" position="after">
            <div class="col-auto col-3 mw-100 mb-2" t-if="o.currency_id" name="currency">
                <strong>Currency:</strong>
                <p class="m-0" t-field="o.currency_id"/>
            </div>
            <div class="col-auto col-3 mw-100 mb-2" t-if="o.rate" name="rate">
                <strong>Exchange rate:</strong>
                <p class="m-0" t-field="o.rate"/>
            </div>
        </xpath>
    </template>

</odoo>