We analyze the long-wavelength features of near-surface composition profiles of monomers in a binary, symmetric blend using a recently developed density functional formalism for polymers in nonuniform environments. Relative to simpler theories of polymer-surface adsorption, our theory predicts a small increase of the interfacial width. We illustrate a derivation of a surface-boundary condition on the composition profile directly from the monomer-surface Hamiltonian. This boundary condition, when combined with our density functional analysis, leads to first-order wetting transitions.