If you are building for Indian users, sooner or later someone asks for "Aadhaar eSign": the signer gets an OTP on their Aadhaar-linked phone, signs the PDF, and the result is a valid electronic signature under Section 3A of the IT Act 2000. Rental agreements, offer letters, loan documents, vendor contracts: they all need it.

Doing it directly means working with an eSign provider's gateway, envelope encryption, and a redirect based signing flow. In this tutorial we skip all of that and use the SignYu API , which wraps the provider (eMudhra) behind a small REST API. We will build:

A route handler that uploads a PDF, adds signers, and sends it for signature.

A webhook route that verifies SignYu's HMAC signature and updates your app when someone signs.

A route that streams the signed PDF's completion certificate.

Everything runs server side in the Next.js App Router.…