When you attach a PDF document to a tax return it is compressed and encrypted, then becomes part of the return data. When you electronically file the return it goes with the return to the IRS or the state (wherever it's attached).
But unlike the tax return forms and schedules, the PDF attachment isn't listed separately for printing in View Results, nor does it print with the return when you select one of the print options such as "One Copy Federal and State". This is normal behavior.
If you need to view a PDF attachment, the menu where it is attached typically has a "View" button that can be clicked to open it in the application associated with PDFs on your PC.