World: r3wp

When printing, the user can often choose to have extra info printed 
with: who ordered the print, date and time, etc. What's the english 
name for this part of the print? The danish word for it translate 
to "receipt", but I feel, there's another english word.

do you metadata ?

Nah, not really. It's been printed typically on a separate page after 
the actual print.

legend
 maybe?

Or that is more used for text under an image in a book?

yes, it is

You can often choose to get this extra info printed as an option 
in the writing program, Notepad, Word or whatever. Or maybe as an 
option in the printer config.

Perhaps "Print job information"  or "Print job summary"

summary
 is a good word, thanks!

they are often broken down into "header" & "footer" in software applications.