How to sign a document in proCertum SmartSign

A practical guide to signing a document with a qualified electronic signature in proCertum SmartSign, from setup and certificate selection to verification and delivery.

Author: Maciej MaciejewskiPublished: 25 October 2026

This guide explains how to sign a document with a qualified electronic signature using proCertum SmartSign. Before you begin, prepare the final version of the file and check what form of signature and method of delivery the recipient requires.

1. Check the document and the recipient’s requirements

Make sure you have the correct file and its final version. Check that the content and attachments are complete, who needs to sign the document, and whether the recipient has specified a required form, type or format of signature. Establish these requirements before configuring the application.

Not every document requires a qualified electronic signature. Check the law, contract and recipient’s instructions to determine the form required for your particular situation. Approval in a system or by email may be sufficient where no stricter form applies; it does not automatically replace a qualified electronic signature where one is required.

2. Prepare your card or SimplySign and configure the signature

You need an active qualified certificate and the proCertum SmartSign application. Download and open the current version of the software.

For a card-based signature, insert the card into a reader connected to your computer.
If you use SimplySign, sign in to SimplySign Desktop with the OTP code from the SimplySign mobile app.

In proCertum SmartSign, open Settings → Signature. Under Signature type, choose an internal or external signature according to the recipient’s requirements. Signature type and signature format are separate settings. If the recipient requires a PDF signature in PAdES format, enable the PAdES option under Additional signature options. Avoid changing other settings unless needed, and follow the recipient’s instructions.

3. Add the document to proCertum SmartSign

Select the Signing tab, then choose Add file. Pick the document you want to sign and check that the correct file appears in the list.

4. Select the certificate and sign

Select Sign. When the application displays the available certificates, choose the correct one and confirm with OK. Check that you are signing the correct version of the document, then authorise the operation with your PIN.

When using SimplySign, remember that the OTP code authenticates you, while the PIN authorises the signature. Enter codes only in the relevant signing workflow.

5. Check which file contains the certificate

With an internal signature, the signed file contains the document and the signature information. An external signature creates a separate signature file, which does not contain the document’s contents. Keep both files and send the recipient the source document together with its corresponding signature file. In proCertum SmartSign, an additional file is created for XAdES or CAdES/ETSI formats when the external signature type is selected.

6. Verify the signature

After signing, use the verification function in proCertum SmartSign. Check that the application recognises the signature as valid and that the document has not been changed since it was signed. Open the resulting file and make sure you have kept all files required for the selected signature type and format.

7. Send the document as agreed

Send the file or files using the method specified by the recipient. For an external signature, attach both the source document and its corresponding signature file.

Quick checklist

□ I have the final version of the document.

□ I have checked the recipient’s requirements for the form, type and format of signature.

□ I have selected the correct certificate.

□ I have verified the signing result.

□ I have kept all files required for the selected signature type.

Signing is more than confirming an operation in the application. Before sending, check the signature and make sure you have all files required by the recipient.