HELP - PDF file comes out blurry on a mac but not pc

My x-boss has a mac and told me he receives these files (PDF) from this one company and when he opens it all the numbers and some fonts are blurry. He prints and it's blurry. He saves on the hard drive and open it blurs.

He send it to me and I see it perfectly.

He opens other pdf from other people and can see it perfectly. For some reason he get's these PDFs from this one company and he is the only one that see blurry numbers.

I told him to access that client from another computer in the mean time I updated acrabat reader.

Does anyone ever had this problem? Can anyone suggest any type of solution?

Thanks!!