Highlight and notes in protected PDF documents in Adobe Acrobat Reader

It is terribly annoying when you buy course literature and you just find out that you can not use highlighter (highlight text tool) or comments in the document because it is protected. Fuck, I've bought the book with my own money and now I want to use it as a real book and mark the text with highlighter pens and pencils!
I do not know how this works in e-readers, but I still read my pdf-books/ebooks in Adobe Acrobat Reader on my computer while I'm waiting to buy an iPad.
It took a while and a lot of googling before I found a way to succeed in getting highlighting and comments to work. I was simply forced to remove the protection with a PDF unlocke.

The program I used and worked really well was the Free PDF Unlocker. To unlock your PDF file you simply drag and drop your pdf file into the shortcut called "PDF Unlocker, drop PDF files here". Then it creates a new PDF file without any protection which you can open in Adobe Acrobat and start adding your highlighted text and comments.