You can't. I have 382 Perception, and there's very, very little for me to add to that until I'm completely maxed on Perception; I have a base 5% on Unspoiled Node items.

It's a pretty big rip-off if you ask me. It'll take a long, long time for those few percentage points to pay off the hundreds of thousands of gil I spent to go from 1% to 5%.