I agree with @Anonymous_ in that the IRS efile system does in fact accept tax returns with pdf attachments.
The issue is that this functionality is typically reserved for more professional tax software packages like CCH Axcess, CCH Prosystem fx and GoSystem; certainly not an all-inclusive list, just those that I am familiar with.
As has been noted, not a current functionality of TT.
*A reminder that posts in a forum such as this do not constitute tax advice.
Also keep in mind the date of replies, as tax law changes.
