One thing you don't do is make copies of them yourself and send them to the medical schools. As a rule and as they should, medical schools distrust letters that do not come from the author directly in an official college envelope; they even prefer, or sometimes require, them from the premedical advisor or committee in official college envelopes, or if there is no advisor or advisory office, the individual writers themselves should write on official college stationary, posted in offical college envelopes. If multiple copies have to be made, faculty have free access to copiers. You should provide postage to the evaluator if requested, but posted official college mail, in college envelopes, is paid for by the college.
There is reason for their caution: enough times in the past applicants have written their own recommendations and been caught at it! Fakery is even easier these days with computers and copiers. Admission folks are neither naive, stupid nor unwary.
