[pdftex] crop marks

[Ronaldo Cristiano Prati]

Sorry if this information was already given on this list, but I can´t
found it anywhere.

I need to put crop marks in a document produced by pdflatex. To do
that, I´m using the crop package by Melchior Franz.

I also need to define the size of the page to 15x21 cm (the final
sheet size), with a mag=750. I´m using the geometry package to do that.

The problem is that the crop marks are out of the page, and it dont apper
both in the screen or printed version. How can I solve it?

The commands I´m using are

\usepackage[pdftex]{geometry}
  \geometry{mag=750,
            truedimen,
            paperheight=28cm,
            paperwidth=20cm,
            left=2cm,
            right=2cm,
            top=1.0cm,
            bottom=1.0cm,
            twosideshift = 0pt}

\usepackage[a4,center,cross,pdflatex]{crop}

thanks

Ronaldo