Print options: How to set crop margins to 0,5cm

[Albacore]

When I was working at local print shop we just set our own crop marks to suit the jobs that we were doing. The reason why the strip out bleed and crop marks is that your file is printed out onto larger paper sizes multiple times in one pass. The print house normally would charge you a small fee for setting out your file and then cutting it to the crop marks.

[cadudesun]

Many thanks for further info guys!
I'm newbie on the matter and your information is of immense value.
Carlos