Problem with attachment to PC

When I sent my attachment (PDF) to my several friends who have PC. They said they opened it blank. By the way I use my AOL Desktop in my IMac to send out. I even sent to myself and open it in my PC. Don't have problem. Can you explain why??

I have IMac 24", Snow Leopard.

Thank you

I don't know why your friends can't receive it OK if you can, but why don't you try without using AOL Desktop and see if it works that way?