Quick answer: Yes - do just that.

Longer answer - Only do it for personal images, to avoid copyright problems (or contact the originator of the mesh for permission); don't expect all the textures to remain intact (.obj format doesn't support things like transparency), and if you add/delete any vertices then any UV mapping will also be lost.

Apart from that, there should be no problems. (I've been doing it for several years for fun and entertainment...)

Cheers,
Diolma