Many a times i read PDFs linked on websites, not knowing whether it is what i wanted (when i am trying to learn something new). In these cases Google comes to the rescue.
Instead of downloading the PDF ,i just google (verb) the link referring the pdf i.e. http://www.hihello.com/hello.pdf
Google would return a “Quick View” link clicking which it returns an HTML version of the pdf, saving a lot of time and bandwidth (money).