How to sign a document with KXCO Sign
Everything you need to upload, sign, send, complete and verify a document — backed by post-quantum cryptography (ML-DSA-65, NIST FIPS 204) and anchored on the KXCO Armature L1 blockchain for permanent, tamper-evident proof.
On this page
KXCO Sign is an online electronic-signature platform built for the post-quantum era. Where mainstream tools rely on RSA-2048 and ECDSA — algorithms a future quantum computer could break — KXCO Sign signs every document with ML-DSA-65, the NIST-standardised post-quantum signature scheme, and anchors a fingerprint of each completed document on a public blockchain so its proof outlives any single company. This guide walks through the whole flow, from your first upload to verifying a finished document months later.
The six-step flow
Create your free account
Go to sign.kxco.ai and choose Get Started Free. There's a free plan and no credit card is required to begin. Confirm your email and you'll land on your dashboard — the home base for everything you send and sign.
Upload your document
From the dashboard, upload the file you want signed. KXCO Sign accepts PDFs directly and converts common office formats (Word, and similar) to PDF automatically, so the version everyone signs is fixed and consistent.
- Drag-and-drop or browse to your file.
- The document is rendered page-by-page so you can place fields precisely.
- Your original is never altered — signing produces a new, completed PDF.
Choose how it gets signed
KXCO Sign supports three signing modes. Pick the one that matches your situation:
- Sign it yourself. Apply your own signature immediately — ideal for a declaration, policy acknowledgement or a document you need to counter-sign.
- Multi-party signing. Add two or more signers. Choose parallel (everyone can sign at once) or sequential (a set order, where each person is invited only after the previous one finishes).
- Guest signing. Recipients sign through a secure signed link with no account and nothing to install. Perfect for clients, counterparties and one-off signers.
Place fields on the page
Drag fields onto the document and assign each one to a specific signer, so everyone sees only what they need to complete. KXCO Sign goes well beyond a simple signature box — see the smart fields reference below for the full set, including required fields, format validation, dropdowns, show/hide rules and calculated values.
Send invitations and sign
Send the document. Each signer receives an email with a secure link. When they open it they see a clean, focused signing view, complete their assigned fields, and apply their signature by drawing it. In sequential mode, the next signer is invited automatically once the current one finishes.
- Signers are guided field-by-field; required fields must be completed before they can finish.
- Format checks catch obvious mistakes (for example, a malformed email or phone number) before submission.
- You can track progress from your dashboard at any time.
Download the signed document and verify it
Once everyone has signed, the document is complete. Download the finished PDF together with its certificate of completion, which records each signer, the time they signed, and the cryptographic proof. To confirm authenticity at any point in the future, head to verify.kxco.ai and check the document — no account, no fee, and no dependence on KXCO staying online.
Smart fields reference
Fields are how a document collects what it needs. Drag any of these onto the page and assign it to a signer:
- Signature & initials — the signer draws their mark; each is bound to that signer's identity.
- Full name & date — captured cleanly and consistently.
- Text — free text, with optional format validation: email, phone, number, postal/ZIP code or government-ID format.
- Checkbox — for agreement and consent boxes.
- Dropdown — let the signer choose from options you define.
- Required fields — mark any field mandatory so a document can't be completed until it's filled.
- Conditional fields — show or hide a field based on what a signer entered elsewhere (for example, reveal a follow-up question only if a box is ticked).
- Calculated fields — compute a value live from other fields (totals, sums) and display it read-only.
How the security actually works
This is what sets KXCO Sign apart, so it's worth understanding in plain terms:
- Post-quantum signatures. Each signature is produced with ML-DSA-65 (CRYSTALS-Dilithium), standardised by NIST as FIPS 204 in 2024. Documents signed today stay tamper-evident even as quantum computing matures.
- Self-contained proof. The signed PDF carries its own cryptographic envelope. Whoever holds the document can verify it independently — there's no lock-in to KXCO.
- Blockchain anchoring. On completion, a SHA-256 fingerprint of the document plus a platform attestation is written to the KXCO Armature L1 blockchain (Chain ID 1111). The on-chain record is public and permanent; you can browse the chain at chain.kxco.ai.
- Private by default. Only a hash is public. The document's contents and the signers' identities stay private to the signing parties.
Ready to sign your first document?
Create a free account and send your first document in minutes. No credit card required.
Get Started Free See the Data Room guideFrequently asked questions
Is a KXCO Sign signature legally binding?
Yes — signatures are advanced electronic signatures, legally binding under the U.S. ESIGN Act and the EU eIDAS regulation, each carrying a tamper-evident cryptographic proof.
What does "quantum-secure" mean here?
Every signature uses ML-DSA-65 (NIST FIPS 204), a post-quantum scheme designed to resist future quantum computers — unlike the RSA/ECDSA used by older e-signature tools.
Do my recipients need an account?
No. They can sign as guests via a secure link, with nothing to install.
How do I verify a document later?
The signed PDF is self-contained. Anyone holding it can verify it at verify.kxco.ai for free, even if KXCO's servers are offline.
Is there a free plan?
Yes — start for free with no credit card. Paid tiers cover higher volume and team features.
Can several people sign the same document?
Yes. Add as many signers as you need and choose parallel or sequential order.