If you say *map* instead of *embedding* and measure area *with multiplicity*, then the problem becomes more interesting.

The following analog of Nash--Kuiper theorem was proved by Gromov in his "Partial differential relations":

>Let $f\colon M\to N$ be a short map between Riemannian manifolds of the same dimenssion. Then there is arbitrarily close length-preserving map $f_\varepsilon\colon M\to N$.

The provided map is evidently a maximizer. 
It is not smooth and typically has creases at everywhere dense subset,
but one can smooth it keeping the area nearly the same.