How to upscale a 480p video to a 1080p with minimal quality loss?
You can upscale Premiere Pro footage using the Detail-preserving Upscale effect in After Effects via Dynamic Link. The results will never be as good as actual HD footage, but the Detail-preserving Upscale effect does a great job at scaling footage without losing too much quality.
There's a short tutorial on how to do this at the following link: