One of my associates has been getting my pdf e-mail attachments just fine for some time on her Windows machine. I use Mac OS 10.4.11, and the pdf stuff starts out as two image grabs of a couple of apple .cwk spreadsheets laid on a .cwk word-processor page. This page is made into a "mail pdf" via the Mac print menu "mail pdf" option. So the pdf goes via Apple mail. The oher day, this associate reported that she'd "upgraded" to Windows 7, and my pdf doesn't show up anymore. She said her IT consultant recommended I resort to "iconizer" software.
But I happen to have a gmail account, and she says she can open my pdf just fine if it's attached to a gmail message.
Also, I note that some folks suggest that attaching the pdf to the end of the Apple mail message improves its accessibility. In my Apple mail messages, I'm able to slide the pdf icon around to any position in the e-mail, so I'm unsure how its accessibility is affected by where it happens to appear in the message.