[Scribus] setting a bleed parameter

[ruth moulton]

  Hi,
i have a document which is being printed professionally, i'm about to generate 
a pdf file for the printers.

the printers have asked me to set a 3mm bleed on the document.

I understand this to be set so that the images etc, especially those that are 
intended to go right to edge of the page, will be extended by 3mm at the edge 
of the page so that the printers have this as a margin of error for paper 
placement (if that makes sense!!)

i cannot see an option to do this, could someone help me please ?

many thanks

ruth