If they can see it on the screen, they can scrape it, OCR it, rip it, convert it, screendump it, video it, and a multitude of techniques to see the data.
When putting content online, you perhaps should consider admin time and maintainability over security which is so easily bypassed. PDFs are great for pixel-perfect printing for documents, but often a 2-3 pager pdf, would be better and more accessible and more easily edited/enhanced, if done as a web page resource.
I don't know if this will work for your purposes, but I use PDFTK to withhold copy/paste on PDF documents, and it's just as easy to withold printing or allow degraded printing as well. (Degraded printing looks like the old 9-pin dot matrix printing.)
Obviously as Gavin said, anything can be defeated, and I discovered by accident how to overcome the "disallow copy" command-PM me for that.
PDFTK is at http://www.accesspdf.com/pdftk/ .
A "withhold copying" file is here: http://eslbee.com/transitions.pdf .
As for the PDFTK example, the PDF you linked didn't seem to have any protection at all - I was able to select text and copy and paste it elsewhere just as usual...
I'd used the program for years, and just a few months ago while trying the Ubuntu OS, I discovered its PDF reader opens the protected file just as you said. Sorry for the recommendation.