How to find "printfriendly"-service specific CSS?

Lets start at first with a sample page (it is in german but it doesn’t matter):

[url]http://deutsche-wirtschafts-nachrichten.de/2015/09/03/wettlauf-um-rohstoffe-usa-wollen-arktis-flotte-ausbauen/[/url]

When you look at it then always at the top middle-right side you find a “printer” icon.

When you click on it the content of the article is send to an often-used external online service called “printfriendly”.
This external site receives the CSS specs together with the core text, then prepares a layout, print it as a *.pdf file
and let it download by the initiating user.

The problem is that I don’t like the default print layout.
I prefer e.g. a (much) smaller font and a smaller line-height.

So I am searching for the print-related (!) CSS statements which are responsible for the print-layout.

Later I want to modify them by Javascript or jQuery through e.g. Greasemonkey.
But this is another step.

At first I want to identify the CSS statement in the original web page which are later send to “printfriendly”.

Can someone point my to the css-layout-script (statements)?

Thank you
Peter

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