Hi,

In Odoo, the external_layout_boxed QWeb template is the standard wrapper used for invoices, purchase orders, and other documents. To modify its style, you first need to inherit the template in a custom module or via Studio (if you prefer no-code). In your inherited template, you can override or extend the CSS by adding <style> tags inside the <t t-call="web.external_layout_boxed"> block or by targeting specific classes. The CSS “path” refers to the class or element selectors defined in the QWeb template. For example, the main wrapper usually has a class like .page, .oe_structure, or .o_main_content. You can inspect these using your browser’s developer tools (right-click → Inspect) to see the exact hierarchy. Once you know the class, you can add CSS rules such as font-size, color, padding, or margins. For example, to change the header font, you might write .page h2 { font-size: 18px; color: #333; }. After modifying the template or adding custom CSS, update the module and refresh the invoice PDF to see the changes.

Hope it helps