How to use Signnow API to automate digital signature collection in custom applications

If you’re building your own tool—or wrangling business processes—and need to collect digital signatures, you’ve probably run into the usual headaches: chasing PDFs, emailing stuff back and forth, waiting days for one click. Not fun. The good news: you don’t have to duct-tape it together. Signnow offers a pretty robust API that lets you bake e-signatures right into your app or workflow.

Here’s how to actually do it, step by step. This isn’t one of those posts that just parrots the API docs—this is what you’ll run into in the real world, what works, what’ll waste your time, and how to get signatures flowing automatically.

Who This Guide Is For

  • Developers building custom apps or internal tools who want to automate digital signature collection.
  • Product teams who want tighter control over user experience (not just sending people to a 3rd-party portal).
  • Folks who are tired of manual signature “workflows” and want to make things actually work without a bunch of hacks.

If you just want to upload and send one contract a month, honestly, just use the Signnow web app. This is for people who want to build automation.

Step 1: Decide If the Signnow API Actually Fits

Let’s get real: APIs sound great, but not every “API” is equally sane or developer-friendly. Here’s what Signnow’s API does well:

  • Embedded signing: You can keep users in your app, no random redirects.
  • Templates: Create reusable document templates.
  • Event webhooks: Get notified when stuff happens (signed, viewed, etc).
  • OAuth2 authentication: Standard stuff, no weird home-brewed auth.

But here’s what you should watch out for:

  • No free lunch: You’ll need a paid API plan. Trial tokens are limited.
  • PDF templates only: You’re prepping and positioning signature fields on PDFs. No drag-and-drop form builder in your app.
  • Occasional API weirdness: Docs are… not always crystal clear. Expect to do some trial and error.

If you’re okay with that, let’s keep moving.

Step 2: Get API Access and Tokens

You need a Signnow account with API access. Don’t skip this or you’ll waste hours fiddling with authentication.

How to get set up:

  1. Create a Signnow account (paid plan with API access).
  2. Register your app in the developer portal. This gives you a client_id and client_secret.
  3. Get your access token using OAuth2.

Quick and dirty: bash curl -X POST https://api.signnow.com/oauth2/token \ -d "grant_type=password&username=YOUR_EMAIL&password=YOUR_PASSWORD&client_id=YOUR_CLIENT_ID&client_secret=YOUR_CLIENT_SECRET"

This gives you a JSON payload with your access_token—use this in the Authorization: Bearer header for all API calls.

Pro tip: Don’t hardcode credentials. Use environment variables or a secrets manager. And never, ever put them in client-side code.

Step 3: Prep Your Document Template

The Signnow API works with PDFs. You upload a PDF, then tell Signnow where signature fields go.

Here’s how to prep:

  • Use a PDF editor to create a clean, fillable form. No weird fonts or layers—keep it simple.
  • Decide where signatures, initials, dates, etc. actually go.
  • Save a “template” copy. You’ll upload this to Signnow once.

Uploading the template via API:

bash curl -X POST https://api.signnow.com/document \ -H "Authorization: Bearer ACCESS_TOKEN" \ -F "file=@/path/to/your/document.pdf"

You’ll get back a document_id. Save this. You’ll use it for adding fields and sending for signature.

What not to do: Don’t try to dynamically generate PDFs and upload on the fly unless you absolutely have to. It’s slow, it’s error-prone, and debugging field positions is a pain.

Step 4: Add Signature Fields to the Document

Signnow calls these “field invites.” You’re telling it: “Put a signature box at X/Y for this signer.”

You need: - The document_id from upload. - X/Y positions for each field (in PDF points, not pixels). - The email(s) of your signer(s).

Sample API call: json POST https://api.signnow.com/document/{document_id}/invite { "to": [ { "email": "signer@example.com", "role": "Signer 1", "order": 1, "fields": [ { "type": "signature", "x": 100, "y": 500, "width": 120, "height": 40, "page_number": 1 } ] } ], "from": "your-email@yourcompany.com", "subject": "Please sign this document", "message": "Let me know if you have questions!" }

Note: The X/Y coordinate system is bottom-left origin (PDF standard), not top-left like HTML/CSS.

What works: - Test on a throwaway PDF first. The field positioning is trial and error. - Use the Signnow web UI once to get a feel for how fields map, then copy values into your API calls.

What doesn’t: - Don’t try to get “pixel-perfect” positioning from your design tool. PDFs are… quirky.

Step 5: Send the Signature Request (Invite)

Once fields are set, you send an “invite”—this triggers the signature flow.

  • You can send via email (the usual way), or
  • You can do “embedded signing” in your app (keeps users in your UI).

For embedded signing:

  1. Generate an “invite” as above, but set "email": null if you don’t want to send an actual email.
  2. Use the API to get an embedded signing link: bash POST https://api.signnow.com/link { "document_id": "YOUR_DOCUMENT_ID" }

This returns a unique URL you can iframe or redirect users to.

Gotchas: - Embedded signing is only available on higher-tier plans. - You have to keep track of invite IDs and document IDs—don’t lose these.

Pro tip: If you want to show real-time status to users, set up webhooks for document.completed, document.viewed, etc.

Step 6: Track Status and Handle Signed Docs

You’ll want to know when the document is signed, and probably download the signed PDF for your records.

Poll for status: bash GET https://api.signnow.com/document/{document_id} Authorization: Bearer ACCESS_TOKEN

Look for the status field (pending, signed, etc.).

Or, better—use webhooks: - Register a webhook endpoint in your app. - Set up Signnow to POST to your endpoint on events (document.completed, etc.). - Handle the event and trigger whatever you need (e.g., notify your backend, update a dashboard).

Download the signed PDF: bash GET https://api.signnow.com/document/{document_id}/download Authorization: Bearer ACCESS_TOKEN

You’ll get the signed file. Save it, email it, archive it—whatever your workflow needs.

What to ignore: Don’t bother with polling every few seconds. Webhooks are way more efficient and reliable.

Step 7: Integrate, Automate, and Handle Errors

You’ve got the basic flow. Now, wire it up:

  • Build a backend service/script that triggers the above steps.
  • Store all the IDs (documents, invites, users) in your database.
  • Add error handling—API calls will fail sometimes (expired tokens, malformed payloads, etc.).
  • Log everything. When something goes wrong, it’s usually a missing field or a bad coordinate.

Real-world advice: - Start simple. Get one end-to-end signature working before you try to automate a whole workflow. - Don’t try to build a generic “sign any document” tool out of the gate. Templatize your most common docs first.

Tips, Pitfalls, and Honest Pros & Cons

What’s great: - The API is powerful and (mostly) predictable. - You control the user experience—no sending people to a clunky portal. - Embedded signing is slick when it works.

What’s not: - Documentation can be sparse or outdated. You’ll need to experiment. - Error messages aren’t always helpful. Sometimes you’ll get a 400 with no details. - PDF field positioning is fiddly. Plan for some trial and error.

What to skip: - Don’t try to DIY your own signature capture unless you’re in a super-niche use case. Legality and compliance are tricky—let Signnow handle it.

Wrap-Up: Keep It Simple, Iterate Fast

Automating digital signature collection with the Signnow API isn’t rocket science, but it’s not plug-and-play either. Get a basic setup working, test with your real docs and real users, and iterate from there. Don’t overthink edge cases at first—solve the main workflow, then add bells and whistles if you really need them.

If you run into snags, check the API docs, poke around community forums, and—when in doubt—try the same call in the web UI to see what’s different. Real-world API work is 50% reading docs and 50% trial and error. Keep calm, keep it simple, and you’ll get signatures flowing without the usual mess.