Templates for sales invoice

Hello Team,
Is there a way to develop a template for sales invoice that could have a different look and add other features on the template?
I will appreciate any guide or support assistance.

Thank you.

Use a custom theme. However, understand that the developer has moved custom themes to the Obsolete Features category under settings and removed all information about them from the Guides. He plans eventually to replace their use with something else. So development effort may be wasted. Themes are written in Liquid. Further, themes change the appearance of forms. They do not add content.