I think this started happening when I downloaded acrobat viewer but I've since deleted but the behavior still persists. Viewing PDFs in Safari is nearly unusable. It's very choppy and skips from page to page from just a slight movement on the trackpad. Also, heres a picture of some mysterious windows that show up in Mission Control when I'm viewing PDFs in Safari, and notice that they are on my desktop, yet Safari is in other spaces. I'm hoping someone knows how to help.