Workaround: set text manually on ToolTipTextNeeded event.
 private void Form1_Load(object sender, EventArgs e)
        {
            this.radPageView1.ToolTipTextNeeded += new Telerik.WinControls.ToolTipTextNeededEventHandler(radPageView1_ToolTipTextNeeded);
        }

        void radPageView1_ToolTipTextNeeded(object sender, Telerik.WinControls.ToolTipTextNeededEventArgs e)
        {
            RadPageViewStripItem item = sender as RadPageViewStripItem;
            if (item != null)
            {
                e.ToolTipText = item.Text;
            }
        }