Note :
Make sure the signature feature is activated. Go to Home > Menu > TOOLS > Settings > Features > Signatures > Activate “Enable signature”
  1. Open an invoice, go to Home > Sales > Choose an invoice.
  2. Tap on the “Pencil Icon” > Signature.
  3. Enter the customer’s signature.
  4. Then choose the Signed by.
  5. Enter additional message on the “Sign text” field

You have successfully captured a signature to an invoice, and will be included in the pdf printout.