The .PDO files are the printable templates, they are just designed to be open with the Free* Pepakura software. They can also be opened with ArmorSmith/TheArmorGarage.
*Pepakura is free to download, but if you want to save any changes to the .PDO file, such as scaling or arrangement, you will need to purchase an optional software license.
tamasoft.co.jp
I also wanted to ask if there’s a tutorial on how to put everything together?