We've answered your question on Apr 19, 2013 - 08:02 and you've replied on Apr 19, 2013 - 08:24. As mentioned in my reply - we unfortunately don't have such option in our iOS app, but you can duplicate tasks in a project through the web.
If there's anything you'd like to know, please let us know and we'll gladly help you anytime :)
Yes, but what if you aren't behind a computer and on a mobile where you don't have WiFi?
Unfortunately, there are no other options to duplicate a project in Todoist, but we will consider adding such feature in future development. You're welcome to add a request to our Votebox: https://todoist.com/Vote_iOS/