Linked PDFs in a PPT in OS X open in Word?

[kumquat]

I am helping a friend with a Powerpoint presentation on OS X. She's putting a hyperlink to a PDF on a slide. When we click on it, Word tries to open it. Adobe Reader is set as the default PDF viewer - when we double click the file itself it opens in Adobe Reader.

Anyone know why Word might be trying to open it and how to stop it?