Polylactic acid (PLA) is a promising biopolymer for environmentally friendly coating development. However, its UV radiation resistance has not yet been sufficiently studied, particularly in formulations containing plasticizers or fillers. In this study, a series of samples were prepared: pure PLA films, PLA films with plasticizers, filled composites, and films obtained from aqueous PLA dispersions. The samples were tested for UV resistance and characterized using FTIR spectroscopy, surface energy analysis, and topography. The results showed that UV irradiation of pure PLA caused carbonyl band broadening and a shift toward lower wavenumbers, water contact angle decrease and surface energy polar component increase. The effect of plasticizers was chemical composition-dependent; epoxy linoleic acid increased the degradation rate, whereas PEG-400 and menthol oleic acid reduced the carbonyl groups accumulation. Menthol oleic acid demonstrated the strongest stabilizing effect. The calcite and kaolin fillers promoted surface oxidation and hydrophilization, while coffee grounds biochar reduced the degradation rate. Films obtained from aqueous dispersions were the most sensitive to UV aging, as residual emulsifier significantly enhanced surface hydrophilization.