The new site should produce output (HTML, CSS, etc.) that is compatible with printing in a typical browser (Chrome, Firefox, Safari, plus whatever Microsoft considers “standard” these days).
SE on Firefox and many sites on many browsers (varies a lot) will do some variant of:
Print only the first page
Print only some headings but not the actual content
Print text but not images
etc.
A print of a Question should include all the Answers (some sites make you scroll down to “live load” more stuff, which is often a problem for printing) and not waste tons of space due to formatting around menus, toolbars, footers, social media widgets (can we just leave those out altogether, please) etc.
There are often problems in JS heavy sites as well where the printing defaults back to a non-JS mode (which is OK) but loses content in the process.
It is MVP because I believe any functional information-packed web site should be printable - whether it is to have notes on hand (e.g., DIY can lead to a trip to Home Depot, having the details of what you need to buy is helpful), show your boss (e.g., “Hey boss, you ignored my email about why the ‘xyz’ method we’re using for securing the database isn’t good enough, let’s sit down and discuss it” and be able to hand him the Q&A that explains it all). etc.
It is different from PDF because it relies on the browser for much of the formatting, margin settings, etc. That makes it far simpler for the server side (basically “make sure the HTML & CSS don’t cause problems for printing” but no extra coding) but makes it less reliable because a ton of browser issues (differences in rendering between browsers, user-configured resizing, browser configured margins, interaction with plugins, etc.) can cause a printed page to not come out exactly the same on every computer/browser/etc. There are other advantages of PDF as well - e.g., able to email the output as a file and know the other person will see exactly what you see. But because of the extra work, PDF is not MVP.
Echoing @gilles’ thoughts about this being above minimum required, though nice to have. If it’s something that needs tested and possibly things changed as a result of that testing it it will require nonzero effort and potentially code.
Is there a low-impact/standard-conformant way of doing it?
There’s probably libraries out there (whether it be client-side or server-side) that do exactly what we’re looking for, but I don’t think we should be worrying about printing pages until we actually get some pages.
For printable (as opposed to PDF), this should not require extra libraries. Just some planning in the HTML/CSS and, yes, some extra testing (which I’d be happy to do).