There's been a translate button for years which hooks deep into every nook and cranny of the website's HTML. It works great, it's built in and many restaurants even advertise it for tourists, because it's a zero-effort translation of their existing menu. Plus, it's low-data when you're inside a 1-bar basement restaurant.

Using an LLM to translate the visible part of a PDF on a mobile... seems like the worst possible solution to the problem.