Is unpublishing and publishing again the only way? What happens to people who have already downloaded it for free? Do they get the updates?

Thanks

As I see for PhoneInfo (our app), which is free, I cannot set is as a paid app.
I think that if you remove the app from the market, the final customer will not be notified....so if you remove the app and put up a paid version, old user will got che old app and they could not be noticed about the new app.

It's my personal opinion, curious if anybody else got a better explanation