Creating the printer friendly version of a web page is done using CSS. Everything except the CSS will be the same for the screen and print versions of the page with the media attribute determining which CSS to use.
Just because someone visits the page doesn't mean they are going to print it and there is no way to tell from within the web page whether your visitor does or doesn't select to print the page as there is nothing changed within the page when they decide to print it.
A partial solution would be to prodvide a print button that will lead to the pdf version of the page for printing, then you could at least track each pdf download - not really 100% the act of printing but at least an intention to print. But pdf's are not practical for normal web pages, they are more suited when a certain strict page layout on paper is required like bank statements, reports, etc. And as felgall said, you will not be able to tell if someone prints the page using File->Print - well, you could disable this way of printing using print css (some display: none, etc.) so that the only way is pdf but that would be kind of user-unfriendly.