Hi,

You can customise it using Odoo Studio or you can edit the template code.

Please refer to the blog to understand how to customize a report using the studio.

https://www.cybrosys.com/blog/how-to-create-custom-reports-with-the-odoo-studio-module

If you want to edit through code, the template name is report_invoice_document, you can see it under technical -> views. You can edit it using Xpath.

Hope it helps