I was taking a look at the Errata, and was curious what was meant by this

" • Perplex may be used by more than one character per turn on a single character’s given combat value."

I always assumed that one perplexer could add +1 to any other character, but just once per round, per perplexer.

Thats right isnt it?

You're right. The errata entry just means that two or more Perplexers can affect the same combat value on the same target character (though said combat value would still be subject to the rule of three).

All it is saying is that if you have two or three perplexers, each could use perplex on the same value of a given character (Perplexer #1 can add to character X's attack value, and perplexer #2 can also add to character X's attack value).
Each perplexer can only use perplex once, but they can all target the same value on the same character (subject to the rule of three).