Foxit pdf reader is worth it if you're careful not to let the aggressive adware in alongside. It's much faster than Adobe's reader and allows you to type real notes that show on the page.
The virus-spyware-adware arms race and the money you have to spend keeping it at bay have turned me off a bit regarding computer land. It's gotten steadily worse over the years. Really, given that biological viruses evolved naturally, using the term "virus" for the computer equivalent is a misnomer. There's a criminal mind behind each one.