Relabel the footer buttons on flow screens.
This component does something simple: it replaces the normal footer buttons with buttons that you get to name. (Right now, that's it, although we have ambitions...)
Set the Next Label and Previous Label to text of your choice. This component doesn't know when it's on the first page or the last page, so you need to tell it: if you put it on the first page, set the "On Start Page?" to the Global True constant. Likewise if it's on the finish page.
And for God's sake, remember to click off the standard Footer using the checkbox in your flow screen configuration.
Want to change the appearance? Someday this component will allow you to add configuration values at design time, similar to Horizontal Rule. For now, know that once you've installed this, you can go to its Style page in Developer Console and tweak the CSS: