Currently you can only print the complete ticket - even if it has 100 or more articles - or a single article. But what can you do when you are interested in three of 100 articles? You can use this add-on.
It adds a checkbox to every article in the ticket zoom. And when you click on the "Print" link in the ticket menu it is checked whether some articles are selected or not. If some articles are selected, those articles are printed.
The code repository and a bugtracker are available at http://github.com/reneeb/otrs-PrintSelectedArticles.