I'm looking at the email source on my PC, and there are differences between sender whose pdf attachments do come through on N9 and hers who don't.

When looking at the breaks between text/html/attachments, the 'good' messages separates section with '------=_Part_ . . .' and the bad has '----boundary_ . . . '

Also, the good one has a field called 'Content-Disposition'. Bad does not.

I'll see what I can do anonymizing the source, but I realize I'm pretty naive about smtp.

And both senders are probably using some form of Apple product, this being a school setting which has been Apple-centric in much of the US even before the Mac arrived.