Digitally sign a PDF with a certificate
eSign PDF on ilovspdfs applies a certificate-based digital signature using your own PKCS#12 bundle, so a reader can verify who signed and detect any later change. It is distinct from the visible stamp of Sign PDF, and runs on ilovspdfs servers as part of Pro: file and certificate are used in memory and never stored.
Pro tool. The file is sent over HTTPS, processed in memory, and never stored.
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About this tool
This is the other thing people mean by signing a PDF, and it is a different mechanism from drawing a signature. A cryptographic signature binds an identity to the exact bytes of the document: a reader shows who signed and warns if a single character changed since. You supply the certificate and private key as a .p12 or .pfx bundle with its passphrase; the signature is computed and embedded as an invisible signature field that appears in the reader's signature panel. Whether the reader shows it as trusted depends on who issued your certificate, not on us: a self-signed certificate shows as unknown until the recipient chooses to trust it. There is no timestamp authority yet, so the signing time is the one your certificate asserts.
How to digitally sign a PDF with a certificate
- 1Choose the PDF to sign.
- 2Add your .p12 or .pfx certificate bundle and its passphrase.
- 3Download the signed document and check it in your reader's signature panel.
At a glance
| What it does | Sign a PDF with your own certificate so readers can verify it. |
|---|---|
| Where it runs | Sent over HTTPS, processed in memory, never stored |
| Accepts | |
| Files per job | One at a time |
| Maximum file size | 4 MB |
| Price | Part of Pro. Needs an account and a subscription; no watermark. |
| Status | Working |
Questions
- Is my certificate uploaded?
- Yes, together with the PDF, over HTTPS. The bundle is opened in memory with the passphrase you give, used once to compute the signature, and discarded with the response. Neither the key nor the passphrase is written to disk or logged.
- How is this different from the Sign PDF tool?
- Sign PDF draws a picture of your signature onto the page, exactly like printing and scanning; it runs on your device and proves nothing about who applied it. This tool attaches cryptographic proof bound to the document's bytes. Which one a document needs depends on what it is for.
- Will my reader show the signature as valid?
- It will show that the document has not changed since signing. Whether it also shows the signer as trusted depends on the certificate: one issued by an authority the reader trusts is shown as valid, a self-signed one as unknown until the recipient adds it to their trust list.
- Why does this tool need a Pro subscription?
- Because it runs on hardware we pay for. Everything that runs in your own browser stays free with no account, at any file size. The cloud tools are the few jobs a browser tab genuinely cannot do, and Pro is what pays for the machines that do them.
Also called Digital signature on a PDF, PAdES signature, Certify a PDF.