On my personal website I have an "About" page. At the top of it there is a "Download CV" link.
Should I put the type of the document in the brackets like "Download CV (PDF)"? Does the lack of extension affect usability?
Yes. Just speaking as a user, please provide me with a clue as to what to expect. I don't mind the extra 3 letters.
Just speaking on my personal experience, I'm tired of pdfs opening in the browser unexpectedly. I want to know if it's a word doc or pdf.
We are in the business of clarity and context, and providing users with clues about what to expect as a result of their actions.