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

[cadudesun]

Hi,

I'd appreciate help.
When exporting PDF, I set "include crop and printer marks..." (snapshot below)
The default crop mark has 1cm in each margin (attached PDF).
However, I need crop mark having 0,5cm in each margin.
I tried to change it in "Print options", but couldn't find how to.
How to set crop margins to 0,5cm?

Thanks for assistance!
Carlos