If you wish to personalize your invoices and make them match your brand style, just click on Your name (bottom left corner) → Company settings → Project accounting → Appearance → Invoice template → Hover over the desired template → Edit.
There you can edit the HTML or add custom CSS code.
If you click on Add from library you will be able to select different languages and set them as default.
TIPS: If you wish to have custom fonts you need to use Google fonts. Here’s an example on how to add the font in the CSS section:
You can also select what fields you want to be included on your invoices and estimates in the customer area.
If you want to make estimates and invoices more personal, you can add custom notes and footers.