Guides

Guides to signing documents you can prove

Answers about electronic signatures: who can read your documents, how to verify a signed PDF, and how to prove a signature or an agreement without sharing it.

• Can your e-signature company read your contracts?

  With most e-signature services, yes: they describe encryption in transit and at rest, not end-to-end encryption, so their systems can decrypt and read your documents. Attest is different: every document is encrypted in your browser before upload and can be opened only by the people you send it to, so Attest can't read it.

• Do e-signature providers train AI on your documents?

  Some do: DocuSign says it trains its AI models on anonymized, aggregated customer data from customers who consent in their contract, and providers that offer AI summaries of your documents read their contents to produce them, even where their policies rule out training. A service that can't read your documents can't train on them: Attest encrypts every document in your browser before upload, so it never has them in readable form, and it has no AI features that process documents.

• How to verify that a signed document is genuine

  A signed document is genuine when you can confirm three things: who signed it, that nothing changed after they signed, and when it was signed. With Attest, anyone can check all three for free and with no account: drop the signed PDF on the open-source verifier it carries, and it checks each signer's passkey signature, the original document, the pages you see and Attest's anchored record on Horizen, a public blockchain, in your own browser.

• How to verify a signed PDF without Adobe Acrobat

  You don't need to buy Acrobat: a certificate-based PDF signature can be checked in Adobe's free Acrobat Reader or an online validator, and some vendors offer their own validation tools. An Attest signed PDF needs none of these, because it carries its own free, open-source verifier, which runs in any browser and checks each signer's passkey signature, the original document, the pages you see and Attest's anchored record on a public blockchain, on your own device.

• How to tell if a document was changed after signing

  Compare the document's fingerprint, a code calculated from every byte of the file, with the fingerprint recorded when it was signed: if even one character changed, the two won't match. Attest's free verifier does this for you: it checks the original document inside a signed copy against what every signer signed, checks each signer's entries, confirms that the pages you see are exactly the pages it re-makes from what was signed and anchored on a public blockchain, and confirms that nothing was added to the PDF after it was sealed.

• What if your e-signature company shuts down?

  A vendor shutting down doesn't change what the parties agreed, but the copies and records it holds can go with it, and the terms of services such as DocuSign and Adobe Acrobat Sign (as published on October 11, 2026) don't oblige them to keep your documents indefinitely after your subscription ends, so the files you download are your evidence. An Attest signed copy proves itself: it carries the original document, the evidence and an open-source verifier inside the file, checked against a public blockchain, so it verifies even if Attest is gone.

• Closed your account? Proving what you signed

  You can still prove what you signed if you kept the signed PDF with its certificate or audit trail; what the vendor still holds depends on its terms, which range from a read-only account to documents it may delete once your account or subscription ends. An Attest signed copy doesn't depend on your account at all: it carries the evidence and an open-source verifier inside the file, and anyone can check it for free, with no account.

• How to prove someone signed a document electronically

  To prove someone signed electronically, you need evidence that they meant to sign, that the signature is theirs, that the document hasn't changed since, and when it happened. Attest builds that evidence into every signed copy: each signer's own passkey signature over the document's fingerprint and their entries, an audit trail inside the sealed copy, and a public blockchain anchor that anyone can check for free.

• "I never signed that": proving an e-signature

  When someone says "I never signed that", the dispute turns on evidence that ties the signature to that person and to that exact document, and the party relying on the document is generally the one who has to produce it. With Attest, each signer approved with a passkey only they control, signing a statement that names the document's fingerprint and their entries, and anyone, including the person denying it, can check that evidence for free.

• How to let others check a signed document

  Give them something they can check themselves: the signed PDF, which carries its own free verifier, or the agreement's certificate link or verification code, which anyone can open for free and with no account while the certificate is public, as it is by default. If they only need to know that you signed it, and the date it was completed, share a zero-knowledge proof instead, so they learn that fact without seeing the document.

• How to prove you signed without sharing the contract

  Share a zero-knowledge proof instead of the contract: it proves that you signed an agreement, or that you and a named co-signer did, and the date it was completed, while the document, its title and its terms stay private. With Attest, every signer gets a proof automatically when an agreement completes, each proof is verified on zkVerify, and anyone can check it for free at attest.datahubz.com/verify.

• How to sign a confidential agreement privately

  To sign a confidential agreement privately, use a service that encrypts the document in your browser so the provider can't read it, and keep sensitive details out of what the service and the signing emails still carry in readable form: the title, the file name and your note to the signers. Attest end-to-end encrypts every document for every signer by default, lets you make the agreement's certificate private when you send it, and lets each signer later prove they signed, and the date it was completed, without showing the document.

• Is it safe to upload a contract to a free PDF site?

  For a low-stakes form it is usually fine, but for a contract it is a weak choice: the free PDF-signing sites we checked work on your file on their own servers and keep it there for a time their policies set, and what you get back is a picture of your signature that proves little if the contract is ever questioned. For a contract, use a service that encrypts the file in your browser and records a signature only you could make: Attest can't read your documents, every signer signs with a passkey, your first 2 documents are free, in total, and signing a document someone sends you through Attest is always free.

• What a breach at an e-signature company exposes

  A breach at an e-signature company exposes whatever it stores in a form it can read: account details, the names and email addresses of the people who sent and signed documents, titles and timestamps, and, at services that hold the keys to their customers' files, the documents themselves. End-to-end encryption takes the documents off that list: Attest stores your document and everything signers enter only as ciphertext it can't decrypt, so a breach of its servers would expose information around your agreements, never what they say.

• Does Face ID or my fingerprint get sent when I sign?

  No: Face ID, Touch ID, Windows Hello and your fingerprint only unlock your passkey; the face or fingerprint data stays on the device that reads it, and the website receives a signature from the passkey and a flag saying you were verified, never the biometric itself. When you sign with Attest, what reaches its servers is that passkey signature over the exact statement you approved, which anyone can re-check later; Attest never sees your face, your fingerprint, your device PIN or your passkey's secret.

• How to tell a real signing request from phishing

  Check three things before you click: that you know the sender and were expecting the document, that the link goes to the signing service's own website (for Attest, an address that begins https://attest.datahubz.com/), and that nothing asks you for a password, for payment to see or sign the document, or to open an attachment. Attest adds a check a lookalike page can't pass: your Attest passkey works only on attest.datahubz.com, and a real Attest email never carries an attachment and never asks for a password, because Attest has no passwords.

• Passkeys for signing documents, explained

  A passkey is a pair of cryptographic keys made for one website: the private key stays with your passkey provider (your phone, your computer or a password manager such as iCloud Keychain or Google Password Manager) and is unlocked with Face ID, Touch ID, Windows Hello or your device PIN, while the website keeps only the public key, which lets it check your signatures. For signing documents, that means each signature is made with a key only you control, over the exact document you approved; Attest has every signer sign that way, with no account to create and no password.

• Why a passkey signature beats an email link

  With email-link signing, the proof that you signed is the service's own record that someone opened your link and clicked, and the finished PDF usually carries the service's own seal, not a signature of yours; with a passkey, you make a cryptographic signature over a statement naming the exact document, with a key only you control and after a Face ID, fingerprint or PIN check on your device, and anyone can check it without trusting the service. Attest uses the email link only to invite you: the signature itself comes from your passkey, which can't be used on a lookalike site and leaves evidence that still checks out if Attest is gone.

• End-to-end encryption for documents, explained

  End-to-end encryption means a document is encrypted on the sender's device and can be decrypted only by the people it is meant for, so the service that stores and delivers it holds unreadable ciphertext and no key that opens it. For a business, that turns "we trust our vendor's staff and security" into "our vendor can't read our contracts", and Attest end-to-end encrypts every document sent for signature, for every signer, by default.

• Will a signed document still verify in 20 years?

  It can, if everything needed to check it travels with the file in open formats and the moment it was signed is fixed somewhere public; signatures that rely on a certificate or on the vendor's service usually need their validation data renewed as certificates expire and algorithms age. An Attest signed copy carries the original document, the evidence and an open-source verifier inside the file, built on open standards and anchored on a public blockchain, so in 20 years checking it needs a program that runs the checks, such as a browser, and one public Horizen node to read the anchors.

• How employers prove an employee signed

  An employer proves an employee signed by showing that the signature was the employee's own act, that it covers this exact version of the document, and when it was made, ideally with evidence the employer couldn't have produced on its own, because the party relying on a signature generally has to prove it when it is challenged. With Attest, each employee approves with a passkey only they control, signing a statement that names the document's fingerprint, and the employee, HR, a lawyer or an arbitrator can all check that evidence for free.

• How to prove the date a document was signed

  To prove when a document was signed, you need a time recorded at the moment of signing by someone other than the person signing, tied to that exact document and kept where the signing service can't change it afterward; a date typed on the page or a file's metadata shows only what someone entered. Attest seals each signing time into the statement the signer's passkey signs, which names the document's fingerprint, and anchors it on a public blockchain, whose block time proves the signature existed no later than that moment.

• Proof of existence: proving a file existed on a date

  To prove a file existed, unchanged, by a certain date, record its fingerprint (a SHA-256 hash, a code that changes if one byte of the file changes) with a time recorded where it can't be changed later, such as an anchor on a public blockchain; anyone holding the same file can then recompute the fingerprint and see that it was recorded by that time. An Attest receipt does exactly this: your browser fingerprints the file without uploading it, the fingerprint is anchored on Horizen, and anyone can check the file for free at attest.datahubz.com/verify.

• Can an e-signature company alter an audit trail?

  A service that both keeps the audit trail and holds the key that seals it can, technically, produce a different record, so with services that seal the record with their own key, you rely on the vendor's internal controls and on the sealed copies you downloaded at the time. Attest puts the fingerprint of its audit trail up to completion, not the trail itself, into an anchor on a public blockchain written when the agreement completes, and each signer's own passkey signature names the document's fingerprint, so neither can be changed afterward, by Attest or anyone else, without verification failing.

• How to make sure every party signed the same version

  Send one final file to every signer instead of separate copies, and confirm afterward that every signature is tied to the same fingerprint of that file, a code that changes if a single character changes; that turns "we all signed version 7" from a recollection into a fact anyone can check. On Attest, the document is fixed once you send it, every signer's passkey signs a statement naming its fingerprint, and the free verifier checks the original inside the signed copy against what every signer signed.

• Is an audit trail enough proof on its own?

  Often not on its own: an audit trail is the signing service's record of what happened, and courts can admit it, but when a signature is denied or the document is said to have changed, it is strongest alongside evidence the signer made themselves and proof that the document is unchanged. Attest keeps its audit trail inside the sealed copy next to each signer's passkey signature over the document's fingerprint and a public blockchain anchor, so the trail is one layer of the evidence rather than all of it.

• Is a blockchain-anchored signature legally valid?

  Yes, wherever an electronic signature is valid, but its validity comes from electronic signature law, not from the blockchain: the anchor is evidence that a fingerprint of the signed record existed, unchanged, at a given time, and in most places courts weigh it like other electronic evidence. A few laws address blockchain records directly, among them Arizona, Vermont, Italy and Mexico's new civil procedure code, and none of them makes an anchor proof of who signed, which is why Attest pairs every anchor with each signer's own passkey signature.

• Proving an agreement to a bank, landlord or investor

  Send a zero-knowledge proof instead of the contract: it shows that you, or you and the other party's signer, signed an agreement, the day it was completed and the email addresses it names, and nothing about its terms, its title or any amount. With Attest, a proof is made for you when the agreement completes, and the bank, landlord, investor or employer checks it themselves at attest.datahubz.com/verify, free and with no account, while zkVerify verifies it independently.

• Keep an agreement confidential and prove it exists

  Keep the document end-to-end encrypted, give it a plain title and make its certificate private; then, when someone needs to know the agreement exists, share a zero-knowledge proof that you signed it, alone or with a named co-signer, and the day it was completed. On Attest every document is encrypted for every signer by default, the sender chooses Private when sending or at any time later, and each signer decides who sees their proofs, which never show the terms, the title or any signer they don't name.

• Zero-knowledge proofs for business documents, explained

  A zero-knowledge proof is a short piece of cryptography that convinces anyone a specific statement is true while revealing nothing beyond that statement, so a business can prove a fact about a document without showing the document. Attest uses Groth16 proofs, each verified on zkVerify, to let a signer prove that they signed an agreement, alone or with a named co-signer, and the day it was completed, while its terms, its title and the other signers stay private.

• Proving a signing date to an auditor without the terms

  Give the auditor evidence they can check themselves that carries the date and the parties but not the document: a zero-knowledge proof states that you, or you and a named co-signer, signed an agreement and the day it was completed, and a certificate of completion PDF adds the title and each signer's name and exact signing time, still without the terms. Both are free to check with no account, the proof at attest.datahubz.com/verify and on zkVerify, the certificate with the open-source verifier inside it, and both rest on records anchored on a public blockchain.

• Confidential deals: proving a partnership is in place

  Share a zero-knowledge proof that you and your partner's signer both signed an agreement, with the day it was completed: the recipient sees your two email addresses and that date, and never the terms, the title or any other signer. With Attest, every signer can make these proofs from the signed agreement on any plan, so agree with your partner first who may share one, and use a short confirmation letter, signed by both companies, when a recipient needs to see one specific term, such as a territory or an end date.