By Tim Kenneally LOS ANGELES (TheWrap.com) – "Pretty Little Liars" racked up some pretty big numbers with its summer finale Tuesday. The ABC Family series pulled in 3.3 million total viewers, making it the most-watched summer finale in the series' history, and a season high for total viewership. In the 18-49 demographic most important to advertisers, "Pretty Little Liars" drew 1.8 million viewers – also a high for summer finales and a best for the season. …