How / What do you want to integrate? SN has open API's that make integration generally straightforward. I know that Pega can interface with API's and Webservices so that is the typical integration point. If you are talking about having ServiceNow as a Customer or Employee portal and you want to expose a Pega process to that portal, it depends a bit on the Pega side but eminently achievable but it "depends" on the Pega side mainly (they have some features that expose processes as applications that you may not own). From the ServiceNow side, likely just a widget or url on the service portal that is open for you to configure.
