Wirelessly printing from phones isn't something that many of us need to do very often. But when you do need to print something then it's frustrating not to find a 'Print' function on an application's menu. However, this little utility may just fill in some of the printing holes in your set-up. As long as an application has graphical content that can be 'shared' through the normal Windows sharing mechanism, then you can share to (ahem) 'Share 2 Print' and this will do what its title claims it can.
This is a free little app which helps printing images from apps that don't support printing natively; but have a sharing functionality.
Share 2 Print is meant to be used through sharing. Starting this app normally will show just an informational screen. Take a look at the screenshots for a walkthrough.
Of course, in practice, it's common to find that application content which can't be directly 'printed' also can't be directly 'shared', but the developer has clearly found this utility useful and it's good to see it available to the rest of us too. Maybe you can keep it tucked away for printing emergencies?
Share 2 Print gets added into the share targets in Windows 10 Mobile, then (right) whatever graphical content you want printed is fired off to the standard Windows printing system.