[Tfug] marking up pdf documents

[christopher]

Does anyone know if there is an app out there that
let's users make marks along the lines of hi-lighting
and comments in pdf documents? With more of my
course materials consisting of digital formats, I
would like it if there was a way to make notes on
them so that I don't always have to print them out
and make handwritten notes.

-- 
christopher <skeptikos at gmail.com>