I've restored a couple film posters for my apartment. Some (unsolicited) advice:

* Do a test print on a small size for the same paper. Color's on the screen will differ to the print (and the print in your room's lighting).

* Use upscayl to bring the resolution up. I aim for at least 300 DPI.

(Plug: check out some of my amateur restorations https://liampulles.com/ )