created links on pdf (work great but my client can't see)

I hope this is a simple question.

I am on a Mac and have a pdf of a newsletter. I open the pdf in Acrobat Pro (9.5.4) and add the hyperlinks to a webpage using the link tool. They work for me great. I then emailed the pdf document to my client who is on a pc and he can't see the links and has no indication that they are there.

He ended up adding the links on his end using the link tool process. Even though this got us through the initial problem I would like to have a solution for future reference.

Any words of wisdom?

(also, I tested the links that my client created on his pdf and they work on my end)