How do I modify the Previous and Next Page posts on blog pages to include “previous” and “next” before the links?

Question

You can do this very easily using the_post_navigation. The WordPress reference page for it has more information.

the_post_navigation( array(
                'prev_text'=>__('Previous: %title'),
                'next_text'=>__('Next: %title'),
            ));

That said, if you do want to continue using `wp_link_pages’ then, again, its WordPress resource is your friend, explaining the parameters and how to change them.

Hope that helps!