A change of your business's details can’t alter your invoices retrospectively, that would create quite a mess in your documents.
If you need to change your business details on a specific invoice, edit the invoice on the Billdu website and select Edit company details. A window will appear where you can edit all your company details for that specific invoice.
If you've added a logo or signature to your Business settings, it will show up on the first invoice you create AFTER such change. In case you need a logo to show up on your invoice, upload a logo to your business settings first and create a new invoice (you can also use the duplication feature)