Abîme is wise, decals are probably what you are looking for.
The only daz clothing with wetness built in are t-shirts, as far as I know. Either you have to edit the textures manually yourself or use decals. Both options are pretty easy to be though.
Texture way: To add wetness to your pants, open the surface tab with your pants selected and find the the glossy and cutout options. You want to create a simple black and white texture you can fill into these slots. This will add a wet glossy reflection and slight see-through at the point you want, giving the illusion of wetness. I recommend GIMP. Use one of the textures in the tab as a base. Super easy.
Decal way: Or just load a decal and position it on the pants.