Welcome to the 405th, Sohan! One of the best resources we have (IMO) is HeavyGunner's All in One Pepakura Pack. It has everything you need to make pretty much anything Halo related, from CE all the way to Reach, and almost all of the weapons and add-ons as well. If this still doesn't work (i believe it's in a zip file or a rar, so it will be compressed), it may be your computer that is having trouble accessing the files. You do have Pepakura Designer installed on your computer, correct? It is the only program that can open .pdo files, and it provides for easy scaling (Pepakura Viewer cannot scale files). In any case, welcome, and I hope this has helped you out a bit!
