How do I insert a downloadable PDF?

What do I need to do to make sure that when a user clicks a word, the external link will go direct to a downloadable PDF? I inserted it but the link won't work. Although, it could be because I'm testing Twine locally. Let me know.

Archaeologists write

[[notes|https://drive.google.com/open?id=0B0sCNgjcw35cazllZmdpTkZEYms/]]

while they're in the field. Your clipboard already contains notes for Test Unit (TU) 7. At the end of your excavation experience, you will be asked to document the following observations about your unit: