However, if it's not a text file, your PDI file may have some sort of readable text within it that explains what type of program was used to create it... and likely open it as well.
Otú ọ dị, ọ bụrụ na ọ bụghị faịlụ ederede, faịlụ PDI nwere ike ịnwe ụdị ederede a na-edegharị edegharị n'ime ya nke na-akọwa ụdị usoro eji eme ya ... ma eleghị anya na-emeghe ya.