You sign by forwarding the email we sent you, the one the document is attached to. There is no account, password, or app.
forward-to-sign@…), and keep the attached PDF.Capitalization does not matter, but keep the attachment: the forwarded email must still include the original PDF, unchanged. Your email provider's invisible signature on that forward is what proves the message really came from you.
Fix it directly on the document’s page while it is still open, no need to start over.
Editing a signer who had already signed simply asks them to sign again (their earlier signature is set aside); the shared document never changes, so no one else is affected.
Your account is where your sent documents live. It is how kysigned knows which documents are yours, so you can track who has signed, receive the completed signing record, and keep your credits (your first 4 documents are free, no credit card needed).
You can prepare a document without signing in: the sign-in moment comes once, when you press Send for signing. A magic link to your email is the whole ceremony; there is no password and no separate registration, your account is created on your first sign-in.
Signers never sign in. The person you send a document to needs no account, no password, and no app: they just forward the email back with the signing phrase, and that is it.
Normally you just press Forward on the email we sent you. If you ever need to construct it by hand, here is exactly what the signing email is:
forward-to-sign@<the kysigned domain>. The exact address is shown in your signing-request email.Signature requested: “Your Document” [ksgn-…]. That [ksgn-…] tag is how we match your reply to the right document, so do not remove it (a leading Fwd: is fine).I sign this document (any capitalisation).Send it from the mailbox the request was addressed to. Your email provider signs the message on the way out (this is called DKIM). That invisible signature, over your words and the attached PDF, is your signature.
Everything you need is inside the one signing-record PDF you received. There are three levels, depending on how thorough you want to be:
Two ways, and they stack. First, the finished signing record is tamper-evident on its own. Drop it on the verify page and the “document matches” check confirms every signer's email is cryptographically bound to the exact PDF they received, your document together with their cover page, and the verification code confirms the whole record is intact. If a single byte of the document had been altered anywhere along the way, verification would fail. So verifying already proves the document everyone signed was not tampered with.
Second, to confirm that document is specifically your file, that nothing was swapped between your upload and your signers, use the hash-check tool. Drop your original PDF on one side and the signing record on the other, and it confirms, right in your browser, that your document is the one carried inside, byte for byte. You can check a sign-request PDF a signer received the same way. It is your own independent check that what went out is exactly what you uploaded, with no need to trust us.
Honestly and precisely: it proves that someone with control of a specific mailbox signed exactly this document, at a time backed by independent timestamps. It is evidence of mailbox control over an exact document, not a claim about the legal identity of a named person.
The proof is your email provider's own signature over your forwarded message and the attached document. Anyone can check it without trusting kysigned: your provider, the public key archives, and the timestamp authorities are the trust set; we are not.
Frankly, charging and accounting for a $0.25 payment by credit card does not make sense: the card-processing fees on a payment that small would cost more than the payment itself. So today you buy a small pack of credits up front (for example, $5 for 20 documents), and each document you send draws one credit. Credits never expire.
Want exactly one document, no pack? That exists today: x402 (an open standard for instant, pay-as-you-go web payments) lets you pay $0.25 for a single document directly, with no top-up and no account setup. AI agents get it built in through the kysigned MCP tools, and any x402-capable client can pay at the API itself; the agent docs show the flow.
Yes. kysigned is open source under the Apache 2.0 license, so you can deploy your own instance with your brand, your domain, and your billing model. It runs on run402, the same platform behind kysigned.com, and every instance produces the same independently verifiable signing records.
See hosted vs your own kysigned for what changes and what stays the same, or start straight from the GitHub repository.
Yes, each PDF can be up to about 3 MB. Larger files are declined when you upload them, with a note to compress or split the document.
It is on the smaller side because every signer's evidence includes a full copy of the document (that is what makes the finished signing record independently verifiable), so it grows with both the file size and the number of signers. If your document is larger, compress it (most PDFs shrink a lot) or split it and send each part for signing separately.
No. Each signing request covers one document, on purpose. You sign by typing “I sign this document”, a single statement of intent, so each request holds a single PDF for that statement to refer to. Allowing several documents would blur what each signer actually agreed to.
If you have more than one, you have two choices: combine them into a single PDF (as long as it is within the size limit above) and send that as one document, or send each document separately.
The document title and signer names we print on the cover and signature pages support Latin (including accents such as é, ü, ñ, and ł), Greek, Cyrillic, Hebrew, and Arabic. Hebrew reads right to left, as you would expect. Arabic letters appear in their standalone shapes rather than joined cursive, so a name stays fully legible even though it is not calligraphically connected.
Chinese, Japanese, and Korean names are not supported yet, because they need a much larger font and extra rendering we have not added. If a name or title uses a character we cannot render, we tell you as soon as you send the document and name the exact character, so nothing is ever printed as an empty box. More scripts may follow.
This limit applies only to the short names we print. The document you upload is never re-typeset by kysigned: its contents travel exactly as you sent them and can be in any language, including Chinese, Japanese, and Korean. Only the name fields on the cover page follow the list above.
Still stuck? Contact the person who sent you the document, or see how signing works.