Growing environmental concerns have accelerated the development of sustainable bio-based films as alternatives to petroleum-derived plastics. Here, agricultural waste was upcycled into functional cellulose/pectin composite films via deep eutectic solvent (DES) pretreatment, mechanical fibrillation, and solution casting. Cellulose-rich fractions were converted into micro-/nanofibrillated slurries to build a percolated fibril network. Pectin and bioactive compounds recovered from the same waste stream were incorporated; pectin acted as a natural binder/network modifier, while ionic crosslinking tailored interfacial interactions to enhance film formation and mechanical integrity. The bioactives provided UV shielding and antioxidant activity without petroleum-based additives. Extraction residues were recycled into the slurries, enabling a resource-efficient, closed-loop process. This work was supported by KOITA grant funded by MSIT (KOITA20250002-18).