How to Sign a PDF with a Digital Certificate

Which kind of signature do you need?

• Sign with Certificate: a digital signature from your certificate, with no mark on the page. Anyone who checks the file sees who signed it and whether it changed afterwards.
• Signature & Certificate: the same digital signature, plus your signature shown on the page in a box you draw.
• Signature: only a picture of your signature on the page. No certificate is used, and nothing proves who signed.

For the first two you need a certificate file (.p12 or .pfx) from your organisation or a certificate provider.

How to sign a PDF with a certificate in Monstera

1. Finish your edits first

   Sign last: any change made after signing shows up as a change when the signature is checked.

2. Open Sign with Certificate

   In the rail, choose Protect, then Sign with Certificate in the Signatures group. To show your signature on the page as well, choose Signature & Certificate and drag a box where it should appear.

3. Fill in the details

   Type the certificate's password, or leave it empty if it has none. Signed by, Reason, Location and Contact are optional.

4. Say what the signature means

   In This signature says, choose I approve this document, or, if you wrote it, one of the choices that begin I am the author, which also say what may still change.

5. Add a timestamp if you like

   In Timestamp, choose No timestamp, DigiCert, GlobalSign or Sectigo. A timestamp proves when you signed.

6. Sign

   Choose Choose certificate and sign and pick your certificate file.

Make the signature visible on the page

With Signature & Certificate, choose how the signature looks: Type it in one of fifteen styles, most of them handwriting; Draw it; Use a picture of it from a PNG, JPEG or scanned PDF; or Use one of my signatures that you kept before. Tick Keep this signature for next time to reuse it; kept signatures stay on your computer.

Good to know

• Your certificate stays put. It never leaves your computer, and its password is not kept.
• Timestamps send no document. Only a fingerprint of the signature goes to the timestamp service. If the service cannot be reached, the document is not signed; try another service or sign without one.
• Several people can sign. Signing again adds a second signature after the first, and both verify.
• Password-protected documents can be signed, and they keep their password and permissions.
• Check a signed PDF with Check signatures: it lists each signer, the certificate's dates, and whether the document changed since signing.

Questions

What certificate do I need to sign a PDF?

A certificate file in .p12 or .pfx format, from your organisation or a certificate provider. Without one, you can still put a picture of your signature on the page, but nothing proves who signed.

Can I add a visible signature as well?

Yes. Signature & Certificate signs the document with your certificate and shows your signature on the page, typed, drawn or from a picture.

Does my certificate leave my computer?

No. Signing happens on your PC, and the certificate's password is not kept. With a timestamp, only a fingerprint of the signature is sent to the service, never the document.

How do I check whether a signed PDF was changed?

Choose Protect, then Check signatures. Each signature says whether the document is unchanged since it was signed, has changed, or had something added afterwards that the signature does not cover.

Full instructions in the Help

• Sign a document digitally
• Add a visible signature
• Check a document's signatures

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