Choose a Proof (Notarize) API authentication method and build a draft-then-add-documents notarization transaction via the Business API

Steps

1. Choose an authentication method for your integration: a static Proof API key, or OAuth Client Credentials for token-based auth - these are documented as distinct setup paths rather than interchangeable options.
2. Create a transaction as a draft (POST /transactions with draft: true and the signers array) when final documents aren't ready yet, instead of requiring documents at creation time.
3. Add documents to the draft afterward via POST /transactions/{id}/documents, referencing a hosted document resource URL and a per-document requirement such as notarization.
4. Finalize the transaction once all signers and documents are attached, and subscribe to Webhooks v2 events keyed by transaction ID to monitor state changes.
5. On each webhook event, call the Retrieve Transaction endpoint for full detail, since webhook payloads typically carry only the event name and transaction ID and not the complete state or document links.
6. Validate the end-to-end flow against Proof's testing tools (in-house-notary test profile, notary/signer platform testing guides) before sending real transactions.