EADI-PFD

Are 'PFD' and 'EADI' abbreviations for the same instrument, and are they used interchangeably? I did not come across the term 'PFD' in either the training manual or the description section of the aircraft maintenance manual. However, in the document I attached to the email I recently sent, it appears the two terms are used interchangeably.

Either term is correct. They represent the same instrument.

What is the situation regarding the EHSI? Can the PFD be used interchangeably with the EHSI, as is sometimes the case with the EADI?"

If the screen sizes physically match, yes.