Can I set up a hand written signature in iOS mail app? Or must I copy and paste each time?
To be able to compose a multiline signature that'll apply to all your messages:


  Settings » Mail, Contacts, Calendars » Signature


Additionally, you can also use:


  Settings » General » Keyboard » Shortcuts


And compose multiple keyboard auto-expanding shortcuts. By using clever shortcut tags (e.g., l1, l2, etc.), you can quickly make multiple lines of text for a seemingly multiline signature.