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Sign a PDF with a digital signature

GOST signature via CryptoPro — inside the PDF with a visible stamp or as a separate .sig file. A free program for Windows; documents and keys never leave your computer.

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What the program can do

Electronic signatureElectronic signature (GOST, via CryptoPro CSP): inside the PDF with a stamp on the page, or as a separate .sig file. You can also sign under a power of attorney (MChD).
Sign a batchMany files at once.
Image signatureDraw it with the mouse or load your own — it is placed with a click.
Check signaturesWho signed, when, and whether the document changed.

How to sign a PDF with a digital signature

Four steps. If CryptoPro and the certificate are already installed — under a minute.

  1. Prepare your signatureYou need CryptoPro CSP and your digital signature certificate — accountants and lawyers usually have them already. Insert the token if your key is on it.
  2. Open the PDF in Construct PDFDouble-click the file or use “Open”. The program is free, no sign-up needed.
  3. Choose “Electronic signature”“Tools” → “Signature” → “Electronic signature (GOST, via CryptoPro CSP)”, then your certificate.
  4. Choose the type and saveInside the PDF with a stamp on the page, as a separate .sig file — or both. Done: the file is ready to send.

Questions

What do I need to sign a PDF with a digital signature?+

CryptoPro CSP and your signature certificate — the GOST signature is created via CryptoPro. Without them, all other features work, including an image signature.

Will the page show that the document is signed?+

Yes, when signing inside the PDF: a stamp with the certificate details is placed on the page. You can customize it — lines, certificate fields, font, colors, logo.

How is a signature inside the PDF different from a .sig file?+

A signature inside the PDF is stored in the file itself and shown as a stamp. A .sig file is a detached signature: the PDF stays unchanged and the signature sits next to it. Many portals ask for .sig. You can create both at once.

Can I sign many files at once?+

Yes — “Sign a batch”: choose the files, certificate, and signature type once, and the program signs them all.

Can I sign by power of attorney (MChD)?+

Yes, the program can sign using a machine-readable power of attorney.

How do I check someone else’s signature in a PDF?+

“Check signatures” shows who signed, when, and whether the document has changed since.

Can I sign with a digital signature online, without the program?+

A GOST signature is created only in the program: the signature key should never leave your computer. Online, right in the browser, you can add an image signature.

Is it free?+

Yes. The program is free: no sign-up, no trial period, no watermarks.

Sign documents for free — no trial period, no watermarks.

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