how do I set margins in Prawn in ruby?

This is what I have so far, but I need to set margins:

def send_fax 
    contact = Contact.find_by_id(self.contact_id)

    pdf = Prawn::Document.new
    pdf.font "Times-Roman"
    pdf.move_开发者_如何学Godown(20)
    pdf.text "ATTN: #{contact.first_name} #{contact.last_name}", :size => , :style => :bold
    pdf.text "RE: #{self.subject}"
    pdf.move_down(20)

    pdf.text "#{self.body}"

    OutboundMailer.deliver_fax_email(contact, self, pdf)

  end

---

Prawn::Document.new( :margin => [0,0,0,0] )

:margin:    Sets the margin on all sides in points [0.5 inch]
:left_margin:   Sets the left margin in points [0.5 inch]
:right_margin:  Sets the right margin in points [0.5 inch]
:top_margin:    Sets the top margin in points [0.5 inch]
:bottom_margin: Sets the bottom margin in points [0.5 inch]

http://rdoc.info/github/sandal/prawn/master/Prawn/Document

---

Just adding to the pantheon of knowledge here, but in case you came here looking to do this using the Prawn Label gem, you can't set the document margin this way. You'll have to do a work around. Here's a quick and flexible snippet for creating a bounding box with a uniform pad that sits inside the document bounding box.

pad = 5

pdf.bounding_box([pad, pdf.bounds.height - pad], :width => pdf.bounds.width - (pad * 2), :height => pdf.bounds.height - (pad * 2)) do
    #Draw all your content in this block and it will be padded uniformly by 5
end

Remove the pdf from .bounding_box and .bounds if you're using an Implicit version of Prawn.