We can use virtual bricks to build various models, but if you prefer papercraft, the following creative app Foldify should be more suitable for you.
Foldify is an innovative and interesting papercraft app developed by Pixle, and designed for iPad. The iPad app features intuitive and simple user interface, and comes with 7 preloaded templates including character, house, car, bus, plants and more. Most importantly, using its editor, you can create your own paper crafts based on the 7 blank templates. In addition to basic pen, brush, color palette, and eraser, there are lots of interesting stickers to customize your papercrafts. After finishing your creation, you can export it as PDF file or directly print via AirPlay printer. Apart from that, you can also share your papercrafts via Email, Facebook, Twitter and Foldify community or get other templates via the community.
Foldify with a size of 25.9 MB is compatible with iPad 2 or later running iOS 5.0 or later. The iPad app is on sale for $0.99 USD. If you’re interested, jump to App Store for more details.