However why email them? Did you try DropBox?
I've been emailing pdf manuals from my desktop outlook express email to my aol email account so I can have them in iBooks on my new Mini. When I get the email pdf it lets me open it in iBooks. But I have a 1 page pdf I made and when I click on the download arrow it doesn't open it the same way as the manuals. It just opens it in the body of the email and won't let me save it in iBooks. It's a lost dog pdf I made just in case.
It worked ok when I sent them all to my iPad2.