Peter Wilson

Many browsers will not render your webpage until the print.css is loaded. Delay Print CSS prevents this from happening. Once your page has fully rendered (including JavaScript, images, etc) your print stylesheets will be loaded.
Using the methods described in a <a href="http://bigredtin.com/behind-the-websites/delay-loading-of-print-css/" rel="nofollow ugc">recent blog post</a> this plugin uses JavaScript, with a non JavaScript fallback, to load your stylesheets last.
If your WordPress site uses jQuery then it is used to load the stylesheets, otherwise the plugin outputs its own JavaScript.

Delay Print CSS

Prevent your print stylesheets from delaying rendering of your website

Adam Harley (Kawauso)

Removes the version parameter from scripts and stylesheets enqueued by WordPress’ <code>wp_enqueue_script()</code> and <code>wp_enqueue_style()</code> functions.

Remove Script & Stylesheet Versions

Removes the ?ver= parameter from enqueued scripts and stylesheets URLs.

Delay Print CSS vs Remove Script & Stylesheet Versions