Signature envelopes
Upload a PDF, set signers and the order — sequential, parallel or mixed groups. Each participant gets a secure, individual link, and can hand their turn over when you allow delegation.
Post-quantum seal · NIST FIPS 204
Close the deal. Keep the proof.
Send the document, collect signatures in the order you define, and walk away with evidence of who signed what, when and from where — that anyone can verify without taking our word for it. Isolation between organizations is enforced by the database, not by application code.
No credit card. 15-day trial with 50 signatures included.
See it in action
From sent to signed, with proof at every step
Watch an envelope go from invitation to a sealed, verifiable signature. Every step is written to the audit trail.
sign.quathos.com
Sent
Services agreement
PDF · 3 Signature
Signature
Envelope sent
Document opened
Identity + signature
Sealed & verifiable
Audit trail
- Envelope sent to Ana Souza
- Ana opened the document
- Identity confirmed · signing
- Signature recorded · sealed with hash
2min
from a PDF on your desk to a request in their inbox
100%
of signing events land in a chain an auditor can check
50
signatures to try it with, free, for 15 days
Everything a signing flow needs
From upload to proof of integrity. No spreadsheets, loose emails or paper.
Smart fields
Signature, text, checkboxes, numbers — plus conditional fields, formula-calculated values, auto-filled name, date and national ID, and file attachments requested from the signer.
Templates and bulk send
Turn a recurring envelope into a template and send it in batch from a CSV — one envelope per row, each tracked on its own.
Public signing links
A fixed URL for your site or QR code: whoever fills in name and email receives the signing invitation in their inbox. Usage limits and expiry included.
Audit trail
Every event is written to an append-only, hash-chained log: who opened it, when they signed, from which IP.
Reminders and deadlines
Set an envelope expiry and automatic reminders. Track what is pending in real time from the dashboard.
True multi-tenant
Per-organization isolation enforced in the database (RLS), not just in the application. One customer’s data never reaches another.
API and webhooks
Tokens scoped to test and production environments. Embed signing into your own product.
Public verification
Anyone can check the authenticity of a signed document with its verification code. No account required.
WhatsApp delivery Coming soon
Signing invitations and reminders delivered where people actually look. Phone numbers are already validated for it.
Three levels of signature
Assurance levels are set by the law that governs your transaction — not by where you are or which language you read this in. Pick the level that law and the document’s risk require.
- Available
Simple
Electronic acceptance recording IP, date/time and device. For low-risk documents between parties who already know each other.
- Available
Advanced
Stronger signer identification (email and SMS/OTP), a cryptographic bind to the document and detection of any later change.
- Available
Qualified — Brazil (ICP-Brasil)
For documents governed by Brazilian law: signature with the signer’s own ICP-Brasil certificate (A1), embedded in the PDF in the PAdES standard — chain validated against the official ITI trust store and revocation checked at signing time.
Levels 1 and 2 are what most transactions need worldwide. Under regimes such as the ESIGN Act and UETA in the United States, an electronic signature is not made stronger by a government-issued certificate — there is no higher tier to reach. Level 3 exists for transactions governed by Brazilian law, where the qualified tier is a distinct legal category.
Security that doesn’t rely on goodwill
A signed document is only worth anything if you can prove it hasn’t changed. That is why Quathos Sign’s guarantees are structural: enforced by the infrastructure, not by code convention.
- Evidence sealed with a hybrid signature resistant to quantum computing — ML-DSA (NIST FIPS 204) + Ed25519, via an audited cryptographic module (OpenSSL).
- Isolation between organizations enforced by the database (Row Level Security).
- Documents are never exposed: every access goes through a short-lived signed URL.
- Append-only, hash-chained audit: events cannot be altered or deleted.
- Passwords with argon2id; API tokens stored only as hashes.
- Every upload is validated before becoming a document; if it fails, it goes to quarantine.
Audit chain
Each event carries the hash of the previous one. Altering an old record breaks the whole chain that follows, and that break is detectable.
- Document uploaded and validated
- Envelope sent to signers
- Signer opened the document
- Signature recorded
- Document finalized
Pricing
We charge per signature — one signer on one envelope. A contract with two signers uses two, however many documents it holds. Unused quota does not carry over.
Free trial · 50 signatures, 15 days
Just you (1 member) · Real signing, no card. Pick a plan when the trial ends.
Starter
$12 /mo
150 signatures / month
Up to 2 team members
For getting started.
- 150 signatures a month
- Public signing links
- Automatic reminders and deadlines
Growth
Most chosen$29 /mo
500 signatures / month
Up to 5 team members
For signing every day.
- 500 signatures a month
- API and webhooks
- Bulk send (CSV)
- Google Drive & OneDrive connectors
Scale
$69 /mo
1,500 signatures / month
Up to 15 team members
For high signing volume.
- 1,500 signatures a month
- Identity verification (KBA)
- Your brand in signer emails
Need more people than your plan includes? Extra members cost $5.67 each per month. Talk to sales
Enterprise · Negotiated volume
Unlimited team members · High volume and specific requirements.
Start signing in minutes
Create your account, upload a PDF and collect your first signature today. 15 days, 50 signatures, no card.