keynote link to a website

I am using Keynote 2013 on a Mac. I tried to link to a pdf-file that is local on my machine in MAMP. I am setting the link as localhost:8888/filename.pdf. But there is a error message that says "couldnt'f find the link. If i call the same link in Safari it works!

What is wrong? How can i link to a local file in Keynote?

Thanks for your help.

Markus