Yes, you can use them on as many web sites as you want, with these provisos:
- you will be using the same configuration for settings such as selected carrier services, handling fees, etc on all your site. Any setting that you set in your account, in other words, will apply across all your sites.
- when using the HTML wizard, you need to select 'popup' or 'new wndow' as window type. When you use these types, the Cart page opens in a new window. Then, when your customer clicks on Continue Shopping, the window simply closes. For the other option, "same window', we use a configured setting to get your customers back to your web site, and this option wont work if your customers are coming to the Cart from multiple web sites.
- you will need to be using the same paypal address- which is also a configured setting- across all your web sites.