A user can easily upgrade from old PivotPage to the new PivotPage without any hassles. Follow the steps below:
In the project with the old control, update the assembly from the References in the Solution Explorer.
Switch to design view, remove the old controls FlexPivotPage and FlexPivotChart from Toolbox and add the new controls, FlexPivotPage and FlexPivotChart.
Add the FlexPivotPage control to the form.
Switch to code view and replace all code lines with FlexPivotPage and FlexPivotChart to FlexPivotPage and FlexPivotChart respectively.
Run your application and make sure that all the functionalities are working as expected.