Document signing API · 25¢ per envelope · No monthly fee

Document signing API: tag a PDF, POST it, get a webhook

The document signing API starts with 25 free sandbox envelopes, no card. Then it's 25¢ per document, flat: tag the PDF, POST it, and the signing link goes out by email and text.

✓No monthly fee ✓25 free sandbox envelopes ✓No credit card

You get a sandbox key on the next screen. Real delivery, not a simulation.

Check your email

We sent a sign-in link to . It is good for 15 minutes, and your sandbox key is waiting on the other side.

Tag, then post

The PDF you already generate is the input

Send a tagged PDF

B64=$(base64 -w0 agreement.pdf)

curl -X POST https://api.esigndev.com/v1/envelopes \
  -H "Authorization: Bearer sig_sandbox_..." \
  -H "Content-Type: application/json" \
  -d '{
    "document_name": "Roof replacement agreement",
    "document_base64": "'"$B64"'",
    "delivery": "both",
    "signer": {
      "name":  "Jane Smith",
      "email": "[email protected]",
      "phone": "+18135551212"
    }
  }'

Type ^S1 where signer one signs and ^D1 where their date goes. Set that text in white on a white background and it disappears for the reader while staying in the PDF text layer where we can find it. Inline base64 covers files up to about 3 MB, which is most generated contracts in a single call. Larger files, up to 15 MB, go through a two-step upload.

How it works

What the document signing API does with your file

We read the text layer, place the fields where your tags are, and send. Your layout stays yours, and changing the document does not mean re-dragging boxes.

Tag the PDF

Put ^S1 where the signature goes and ^D1 where the date goes, in white text. Invisible to the reader, findable by us.

POST it

One JSON request with the file and the signer. Delivery by email, text or both starts immediately.

Get the webhook

envelope.completed lands on your endpoint with a link to the signed PDF and its certificate.

Pricing

What it costs

What	Siglio
Per envelope	25¢
Monthly fee	$0
Per seat	$0
Minimum	$0
SMS delivery	Included, same 25¢
Sandbox	25 envelopes free, no card

You are billed when an envelope is created, not when it is signed. A declined or ignored envelope still costs 25¢.

Questions

What to know before you send the first PDF

What if my PDF has no text layer?

Anchor tags live in the text layer, so a flattened scan has nothing for us to find. Generate the PDF from your own template or HTML rather than scanning one, and the tags are there by construction.

How big can the file be?

Up to 15 MB. Inline as document_base64 up to about 3 MB, and through the two-step upload endpoint above that. Encrypted PDFs are rejected.

Do I have to place fields by coordinates?

No, and you should not want to. A coordinate map breaks the first time someone edits the contract and everything shifts half an inch. Anchor tags move with the text they are attached to.

How do I get the signed PDF back?

The completion webhook fires with the envelope id, and you download the signed document from the API and store it. Build that into your handler on day one, not after someone asks you for a contract from six months ago.

Can one PDF have two signers?

Yes, up to two. Tag with ^S1 and ^S2, send two signers, and signing runs in order. A PDF tagged for two signers has to be sent with two, and the other way round, or the call is rejected rather than silently sending a half-configured document.

Send a tagged PDF in the next ten minutes

You get a sandbox key on the next screen. Real delivery, not a simulation.

Check your email

We sent a sign-in link to . It is good for 15 minutes, and your sandbox key is waiting on the other side.