Digital Signature

Choose your PDF, add your certificate file (.pfx or .p12) and its password, and decide whether the signature should be visible on the page and where. A trusted timestamp is added by default. The signed PDF then shows who signed it, and that it has not changed since, in any PDF reader that checks signatures.

Invisible proof inside the PDF, made with your certificate, that shows two things: who signed it, and that not one character has changed since. If anyone edits the document afterwards, the signature shows as invalid in every PDF reader.

A certificate file, usually ending in .pfx or .p12, and its password. It is issued to you by an employer, a bank, a government office, or a certification authority that sells document-signing certificates. If you were never given one, you probably don't have one. Sign PDF works without it.

Yes. Use Sign PDF to draw, type or upload your signature and place it on the page. That is an electronic signature and is fine for most everyday documents. It can't prove afterwards that the document wasn't changed.

Yes. "Create a free self-signed Digital ID" makes a certificate and a password-protected .pfx file in your browser, and nothing is sent to us. Signatures made with it prove the document has not changed since you signed, but readers show you as an unknown signer, because no certificate authority has confirmed who you are.

Only if your certificate comes from an authority on Adobe's own trust list. That depends on who issued the certificate, not on which website did the signing. With any other certificate, Acrobat shows the signature as valid and the signer as unknown. That is normal and not an error.

An independent time service records when you signed. This keeps the signature checkable after your certificate expires, and proves the signing time did not come from your own computer's clock. Only a fingerprint of the signature is sent to the time service. The document is not sent.

It was expired, not yet valid, cancelled by its issuer, or issued for something other than signing (for example encryption only). The message says which one. A certificate issued by your own company is accepted. Outside checkers may show it as "not trusted", which is normal.

Your .pfx file contains your certificate but not the certificates of the authority that issued it. Export it again, and choose "Include all certificates in the certification path" when saving. Most export dialogs have this option.

No. Both are used once to make this signature and are then discarded. Your private key is never saved anywhere or sent to any other service.

Yes. Each new signature is added without changing what was already signed, so the first signature stays valid when the second person signs. Verify PDF Signature shows every signature separately.

Not directly. Remove the password first with Unlock PDF, then sign. Signing an encrypted file correctly needs the password inside the signing step, which this tool does not yet support.

Yes. Every tool works without paying and without an account. Files can be up to 200 pages and 80 MB, and a run that fails costs you nothing.

No. All tools work without signing in. An account raises your hourly allowance and lets you see what you have processed.

Your file stays on our server only for a short time while it is processed, then it is deleted. It is sent over an encrypted connection. We keep a record that the tool was used, but not the file name or what is in the file.