This has worked in the past, but no longer. I don't get an error but the mail message does not have any attachment. Neither rtf nor Attach PDF works.
System is Mountain Lion 10.8.2. FWIW, Mail has Herald, MailTags, and MailHub added. The former two are recent additions, so if anyone has a like experience, I can try disabling them temporarily.
I can reproduce the problem without any Mail add ons.
This seems to be a bug introduced in 2.0.4.
I just tried with 2.0.3 and Mail rtf and PDF attachments work fine.