API comparison · 25¢ per envelope · No monthly fee

Adobe Sign API vs. Siglio: 25¢ per envelope, no seats

Start with 25 free documents, no card and no licence to assign. After that, 25¢ per envelope with no seats and no minimum, sent by email and text in one call.

✓25¢ per envelope, no seats ✓Email and text ✓API key in a minute

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Next to the market

	Per envelope	SMS delivery	Monthly fee
Siglio	25¢	Yes, included	None
eSignatures.com	49¢	Yes, 9¢ extra per text	None
Documenso	Not published	Not mentioned	$25 to $250/mo, or self-host
DocuSign	Not published	Not on the Starter or Intermediate API plans; eSignature add-on from $0.36 per delivery	$50 to $480/mo (API plans)
Adobe Acrobat Sign	Not published	Not published	Not published for API tiers
PandaDoc API	Not published	Email or SMS listed, price not published	$40/mo Developer plan, 40 documents

Each company’s figures are from its own published pricing page, linked from its name, checked 7 October 2026. DocuSign’s SMS add-on is from its eSignature plans page; its API plans list SMS as “Does Not Include” on Starter and Intermediate. Adobe’s Acrobat Sign API FAQ says API access is “reserved exclusively for enterprise and developer tier accounts” and prices neither. Documenso’s page does not mention SMS. “Not published” means the page does not state it. Prices change; check the source before relying on it. Longer comparisons: DocuSign, PandaDoc, Adobe Sign.

# Tag the PDF with ^S1 where they sign, then:
B64=$(base64 < agreement.pdf | tr -d '\n')

curl -X POST https://api.esigndev.com/v1/envelopes \
  -H "Authorization: Bearer sig_..." \
  -H "Idempotency-Key: order-41882-contract-1" \
  -H "Content-Type: application/json" \
  -d '{
    "document_name": "Roof replacement agreement",
    "document_base64": "'"$B64"'",
    "delivery": "both",
    "signer": {
      "name":  "Jane Smith",
      "email": "jane@example.com",
      "phone": "+18135551212"
    }
  }'

# POST to your webhook endpoint when the last signature is in
{
  "id": "evt_8f3k2m9q1x",
  "type": "envelope.completed",
  "occurred_at": "2026-09-28T15:04:11.482Z",
  "data": {
    "envelope": {
      "id": "env_k7m2v9x3q1",
      "state": "completed",
      "document_name": "Roof replacement agreement",
      "delivery": "both",
      "signer": {
        "name": "Jane Smith",
        "signed_at": "2026-09-28T15:04:09Z"
      },
      "completed_at": "2026-09-28T15:04:09Z"
    }
  }
}

# then fetch the signed PDF, certificate included:
curl https://api.esigndev.com/v1/envelopes/env_k7m2v9x3q1/document \
  -H "Authorization: Bearer sig_..." -o signed.pdf

One POST creates the envelope and sends it. Bearer token, no JWT, no consent screen. The webhook body is trimmed to the fields you act on; the full shape is in the docs.

25¢

per envelope, flat at every volume. No monthly fee, no seats

SMS

and email, or both, in one API call, included in the 25 cents

ESIGN

and UETA, with a certificate page for each signer on every signed PDF

30 days

signed copies are kept after the envelope closes, then deleted

Published figures

What each one publishes

	Siglio	Adobe Acrobat Sign
Price per envelope	25¢	Not published
Monthly fee	$0	Not published for the tiers that carry API access
Per-seat fee	$0	US$16.99, US$23.99 and US$29.99 per licence per month on the published business plans (annual, billed monthly)
Minimum commitment	$0	Not published
SMS delivery	Included at the same 25¢	Not published
Free trial access	Key on screen in about a minute. No card, no account review.	“Register a Developer account”; the terms are not published
Webhook on every event	Every event type, every account	“Webhooks are supported in the REST API v6 and later”; the plans that carry them are not stated
Multi-signer	Two per envelope; signer two is notified after signer one finishes	Not published

Adobe figures are quoted from Adobe's published Acrobat for business plans page and its Acrobat Sign API FAQ, checked on 7 October 2026. The per-licence prices are from the business plans page; the API FAQ states that “API access is reserved exclusively for enterprise and developer tier accounts”, and the price of those tiers is not published. So the published seat prices and the tiers that carry API access are not the same thing, and the table says so rather than implying one price covers both. A cell reading “Not published” is not stated on either page. Prices change; check the source before relying on it.

The thing worth noticing is that the prices Adobe publishes and the tier that carries API access are not the same thing. The per-licence prices above are the business plans; the API FAQ says access is reserved for enterprise and developer tier accounts, and those are not priced on the page. If you need Acrobat itself, none of that is a criticism, it is just a different purchase from an API key.

Switching

Moving a small integration over

Auth is a Bearer token in the Authorization header. No JWT and no consent screen.
One POST creates and sends the envelope: the PDF, the signer, and delivery by email, text or both.
Webhooks are on every account, for every event type. Point one endpoint at them.
The signed PDF comes back by id. On envelope.completed, download it by the envelope id and keep your copy: Siglio deletes it 30 days after completion.

How it works

The e-signature API in three steps

A bearer token, one POST and one webhook. No licence to assign to anybody and nothing to install.

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 the envelope id. Download the signed PDF, certificate included, and keep it.

Pricing

What it costs

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

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

Legal standing

Legally binding, with the record to show it

ESIGN ActFederal, 15 U.S.C. §7001 UETA49 states, D.C., Puerto Rico, U.S.V.I.

Electronic signatures have carried the same legal force as ink in the United States since 2000, under the federal ESIGN Act and, at state level, the Uniform Electronic Transactions Act. Every signed PDF carries a certificate page per signer with the sent, viewed and signed times and the IP address each came from. How the record holds up.

Questions

Reading this one honestly

Why can I not see an Adobe API price?

Because Adobe does not publish one on the pages linked under the table. The business plans page prices licences; the API FAQ says API access is reserved for enterprise and developer tier accounts and does not price them. We are not going to estimate a number and put their name next to it.

How does 25¢ compare to a plan?

There is no plan to compare. 25¢ per envelope, flat, at every volume, with no tiers. $0 monthly fee, $0 per seat and $0 minimum, so your monthly envelopes times 25¢ is the bill.

Do I need a consent screen?

No. Every call carries a Bearer token. No JWT and no consent screen. Your API key is on screen in about a minute, with no account review, and the 25 free documents deliver to real inboxes and real phones.

Is SMS extra?

No. Email and text go out in the same API call at the same 25¢. There is no SMS surcharge.

Is it legally binding?

Yes. Electronic signatures carry the same legal force as ink in the United States under the federal ESIGN Act and state UETA. Every signed PDF includes a certificate page per signer with the timestamps and IP addresses. More on the law.

What are the limits?

Two signers per envelope, signer one first: signer two is notified only after signer one signs. PDF only, up to 15 MB. Signed documents are deleted 30 days after completion, so download the signed PDF by id on the completion webhook and keep it.

Try it before you price anything

25 free documents, no card, no call. The key is on the next screen.

Continue with Google

or use your work email

You get your API 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 API key is waiting on the other side.