Draft: bug(print): Make printed pages compatible to printCreator (and others)

Related to #170

What does this MR do and why?

With printCreator, the margins don't display properly. It is probably the case with other printing widgets / tools

Solutions:

• Make the default 'save as PDF' of the browser by default
• Change all the sizes as rem, so it might be more flexible to other tools (cause I guess the difference is dpi)

Screenshots or screen recordings

How to set up and validate locally (or on alpha)

In ubuntu, you can install

sudo apt-get install printer-driver-cups-pdf

which seems to cause the same issue as PDFCreator