Hello,
You need to replace customer_address div in template: report_delivery_document in ./stock/report/report_deliveryslip.xml
Copy this and replace
<div class="row" name="customer_address">
<div class="col-xs-4 pull-right">
<div>
<span><strong>Customer Address:</strong></span>
</div>
<div t-if="o.move_lines and o.move_lines[0].partner_id" name="partner_header">
<div t-field="o.move_lines[0].partner_id" t-options="{"widget": "contact", "fields": ["address", "name", "phone", "fax"], "no_marker": True}"/>
</div>
<div t-if="not (o.move_lines and o.move_lines[0].partner_id) and o.partner_id" name="partner_header">
<div t-field="o.partner_id" t-options="{"widget": "contact", "fields": ["address", "name", "phone", "fax"], "no_marker": True}"/>
</div>
</div>
</div>