Displaying column totals

Hello, thank you for creating this plug-in – I really enjoy using it!

I want to display column total for fields such as Paypal Fees and Shipping costs in CSV exports.

I found this link in documentation for adding summary to PDF documents but I get the following error:

The code you are trying to save produced a fatal error on line 28:

Cannot declare class Woe_PDF_Summary, because the name is already in use

Are there any hooks that I can use to render a row in the produced CSV file for column totals?

thank you