Take a screenshot of an entire webpage in Opera

You could print the page to a PDF document. This way, the text is rendered using vectors and will hold up much better in high resolution print.

Most print is done in 300dpi. Text will go as high as 1200 or even 2400dpi sometimes. Your screen on the other hand is typically 72 - 96dpi. So, if your page is text-heavy, it'll end up looking a lot sharper and crisper printed compared to its on-screen version.

More information about DPI here: http://www.nikon-euro.com/nikoneuro_en/hit/general/en/HIT_gen_en_17.htm

I ended up using PhantomJS in windows, I used...

screenshot.js

var page = require('webpage').create();

page.open('http://gigantic-web-page.com', function () {
    page.render('test.png');
    phantom.exit();
});

Dump this in your phantomjs folder, then one more file, screenshot.cmd

phantomjs --ignore-ssl-errors=yes --cookies-file=cookies.txt --web-security=no screenshot.js

With both of these files in your phantomjs folder, run screenshot.cmd... I just generated a 40mb png file of a gigantic page, it took a while and churned away but it finally output it!