Professional truck drivers spend prolonged periods seated, often leading to discomfort and fatigue. Conventional seats are typically designed for average body dimensions rather than individual morphology, which limits their ability to provide optimal support. This study investigates whether 3D-printed personalized seat inserts, developed through an integrated digital workflow, can improve pressure distribution and perceived comfort compared with a standard truck seat. Sixteen participants completed the full workflow from body-data acquisition to comfort evaluation in a static truck buck. Unlike existing personalization approaches, the workflow explicitly incorporates occupational context and task-related posture constraints as design inputs, and validates a complete, reproducible end-to-end process combining vacuum cushion molding, 3D scanning, computational modelling, and large-format additive manufacturing. Pressure mapping and subjective comfort ratings were collected for both baseline and personalized conditions. The personalized inserts reduced mean pressure by 39% and peak pressure by 18%, while increasing contact area by 15%. Subjective comfort scores improved significantly across all regions, particularly in the buttock area, with participants describing firmer yet more stable support. Beyond these ergonomic outcomes, the study contributes a context-driven personalization method and demonstrates that geometric adaptation informed by real use conditions yields quantifiable comfort benefits in an occupational transport setting.