voucher_print/voucher_print_report.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>
<report 
            id="voucher_ext"
            model="account.voucher"
            string="Payment"
            report_type="qweb-pdf"
            name="voucher_print.report_voucher"
            attachment_use="False"
            file="voucher_print"
        />
    </data>
</openerp>