RFC render pdf improve page size

About these tests, I think the (limited) diff context shown by github might have been misleading here : the description of the first test is "can capture and save it into a file", and for the second "can capture and save it as PDF into a file".

The changes only aim at making things more coherent (and refactoring in the case of the second test).
I will make a separate pull request for this one if it's actually meaningful to you.