It turns out that the problem was not with the PS23 1040 tax software.  The problem was that the pdf that I was trying to attach to the client's return had become corrupted.  I have never experienced a corrupted pdf in the past, so I did not consider it as a possibility.  

Thank you @IntuitGabi  for having an experienced Intuit troubleshooter call me to help solve the problem over the phone.  I did not catch his name, but he is the real deal!