knowledge/document_page_approval/document_page_view.xml

<?xml version="1.0"?>
<openerp>
    <data>
        <record id="wiki_history_form_inherit" model="ir.ui.view">
            <field name="name">document.page.history.form</field>
            <field name="model">document.page.history</field>
            <field name="inherit_id" ref="document_page.wiki_history_form"/>
            <field name="arch" type="xml">
                <xpath expr="//form/label[@for='page_id']" position="before">
                    <header>
                        <button name="page_approval_approve" string="Approve" states="draft" />
                        <field name="state" widget="statusbar" statusbar_visible="draft,approved"/>
                    </header>
                </xpath>
            </field>
        </record>
        
        <record id="wiki_form_inherit" model="ir.ui.view">
            <field name="name">document.page.form</field>
            <field name="model">document.page</field>
            <field name="inherit_id" ref="document_page.view_wiki_form"/>
            <field name="arch" type="xml">
                <field name="display_content" position="before">
                    <field name="approved_date" class="oe_view_only"/>
                    <field name="approved_uid" class="oe_view_only"/>
                </field>
            </field>
        </record>

    </data>
</openerp>