hide_print_button/stock_view.xml

<?xml version="1.0" encoding="UTF-8"?>
<openerp>
    <data>
        <record id="view_picking_out_form_ext" model="ir.ui.view">
            <field name="name">view.picking.out.form.ext</field>
            <field name="model">stock.picking.out</field>
            <field name="inherit_id" ref="stock.view_picking_out_form"/>
            <field name="arch" type="xml">
            	<data>
                    <button name="%(stock.report_picking_list_out)d" position="attributes">
                    	<attribute name="invisible">True</attribute>
                    </button>
				</data>
            </field>
        </record>
	</data>
</openerp>