You can now set up more than one signature in the new iOS 6 Mail app for your iPhone, iPad, or iPod touch. Each email account you have set up will allow you to have a specific signature attached to just that email address.
Step 1 .Tap your Settings app to launch it
Step 2 . Select Mail, Contacts, Calendars and scroll down to where you see the Signature option and tap it.
Step 3 .The two options on the top are All Accounts or Per Account.Select on Per Account, you’ll get options below to create a signature for each email account on your iOS device.
Now you can create Set Up Multiple Signatures