Send Yourself an Email with Your Signature
Send yourself an email with your desired email signature. Obviously you will need a currently operational signature from another mail program on your computer.
If you don’t yet have an HTML signature, here is some example code to get you started.
(A separate post on how to do this will be coming soon)
Copy Your Signature to the Clipboard
Tap and hold your finger on some part of the email body that is not a link. Drag the little knobs at the end to surround your signature as best as possible. When surrounded, tap “Copy”.
Paste Your Copied Signature
Go Settings > Mail > Contacts > Calendars > Signatures. In here paste your signature for all email accounts, or for each one if you would prefer. Tap twice in the empty box and select “Paste” from the popup menu.
Shake to Undo
Apple tries to “enhance” the signature when you paste it, causing it to become all messed up. Luckily, you can undo these “enhancements”. Shake your device and press “Undo Change Attributes”.