This should get you far enough along to make it work.
sale.report_saleorder_document is the report you want to inherit and override for changing the way the Customer (Partner) is shown.
The QWEB directive that prints the Customer information is:
<div t-field="doc.partner_id"
t-options="{'widget': 'contact', 'fields': ['address', 'name'], 'no_marker': True}"/>
By default Odoo will show Company, Customer with the address - that's how the template for the widget is defined.
There are two changes you will need to make:
1. Remove the name field from the fields key. This shows the address WITHOUT the name.
<div t-field="doc.partner_id"
t-options="{'widget': 'contact', 'fields': ['address'], 'no_marker': True}"/>
2. Show the specific name(s) of the Customer.
<div t-field="doc.partner_id.name"/>
<div><span t-field="doc.partner_id.company_name"/>:</div/>
For a final result of:
<div t-field="doc.partner_id.name"/>
<div><span t-field="doc.partner_id.company_name"/>:
<span t-field="doc.partner_id"
t-options="{'widget': 'contact', 'fields': ['address'], 'no_marker': True}"/>
Note that the quote characters have to be escaped - you will see this in the original Odoo XML, with the original QWEB snippet looking like this:
<span t-field="doc.partner_id"
t-options="{"widget": "contact", "fields": ["address"], "no_marker": True}"/>
Your finished report would then look like this:
Forgot to mention , I need this modification for the PDF report, the model it self I have no problem, with the design