If you don't have the Red Giant suite yet, After Effects has a powerful built-in tool that rivals third-party plugins: Change Composition Settings : Set your width to 3,840 and height to 2,160. Apply Detail-Preserving Upscale
Adjust these to recover lost detail. Experts often recommend a Sharpness of 6 and a Quality of 10 as a reliable starting point. instant 4k plugin after effects
Retooled to be up to 400% faster than its predecessor, Instant HD, making it efficient even for high-resolution renders. If you don't have the Red Giant suite