Yes, they all work as far as I know. Some of them you have to capture and others you have to hire. I can't recall which buttons work for either action.
The rules Robin made (I have a copy of the rules but can't remember where I got it) explain which travelers are hired and which captured. I think the search button works to capture, and hire works to hire.
If you haven't seen it, and I didn't see it for quite some time, there is a button that looks like multi-colored stars on a black amorphous shape way at the bottom of the window you use to record actions. The "star window" is near the button showing the red die. That multi-colored star window shows you all the travelers currently on the board and tells you the benefit you get from interacting with them.