Try extracting "Theorem 2" on page 5, or any text really. I just get random noise through either a PDF reader, or something like pdf2ascii / ps2ascii.
We just made this with standard latex.
I work with course materials made in Latex, and students sometimes need/want to copy and paste from them, so I try to avoid these kinds of problems.
This is just an example. From experience, most PDFs at conferences and journals, generated from pdf, are not accessible to varying degrees.