Tiger intel rejects PDF file

[Patth9]

My friend is using an iMac, don't know which one, but he is still running Tiger Intel. He uses Hot Mail for his email service which is either on Foxfire or Safari. When I send him a PDF from my Mt. Lion Mac Mini, he gets a "warning" notice and can not open the email. Apparently, this only happens when I send a PDF file or my husband sends a PDF from Snow Leopard mac mini. I and my husband use Firefox. BTW. when I send him a simple email, he has no problem.

Can anyone tell me what might cause this? I have my guesses, but would like to consider someone else's guesses.

Thanks for reading my crazy question.

 

[Patth9]

maybe there isn't an answer

Okay, what I think is the iMac does not have the up-to-date PDF reader to accommodate the up-to-date PDFs.

Tiger intel, is not equipped to open a current PDF file either.

And possibly, Tiger Hot Mail is not up to date because Tiger was kicked to the curb a long time ago.

What do you think? It is so hard explaining to people who do not know their computers even a little, why they don't need a NEW computer, but they do need a more up-to-date operating system.