In the Quick Reference (back cover of the Rules Reference), under Hunter Actions, the Trade action is described as follows: "Choose a hunter in the same location. Then, secretly trade event cards with that hunter." [emphasis mine]

In the rules on Trade (page 13 of the Rules Reference), it states "The two hunters can show each other their item cards and ticket tokens and give any of those cards and tokens to each other." [emphasis mine]

This seems to be an error in the Quick Reference.

(Note that Van Helsing's Leader ability does allow the trade of events - and only events).

You are correct. It's an error in the reference. We know this because Van Helsing's special ability is that on a trade action he can trade event cards instead of item cards. Thus it is logical hunters can't trade event cards on a normal trade action.

As of December 4, 2015, this is officially "errata'd" on version 1.0 of the official FAQ, found elsewhere on this site.