Adding Additional Shop Pages
To add additional shop pages go to your main page list and at the bottom there is the option to add a new page, in here you just need to change the page type from "WYSIWYG" to "PayPal Shopping Cart" and then choose the location of the new page if you want it as a sub page to your already existing shop page then select your main shop page in the "Parent" drop down box.
And that is pretty much it, one last thing to check is the Page Settings section within your new shop page and make sure the "Proceed Shopping URL" is set to your main shop page.