Sign a PDF with your digital certificate
Apply a real cryptographic signature with your own .pfx or .p12 certificate. Your private key never leaves your PC.
A real signature, applied locally
A fast, private desktop toolkit — not another website that uploads your files.
A signature, not a picture
An image of a handwritten signature proves nothing. A digital signature is bound to the document and to your certificate, and PDF readers verify it.
Your key stays on your PC
Signing on a website means handing your certificate and its password to someone else's server. PdfForge signs locally, so the key never travels.
Later changes are detected
If anyone edits the file after you sign it, readers show the signature as invalid — which is exactly what a signature is for.
How to sign a PDF with your certificate
4 steps, entirely on your PC.
Download PdfForge free from mes-dev.com and install it on Windows.
Open Sign and choose the PDF to sign.
Choose your .pfx or .p12 certificate, type its password and click Check certificate.
Click Sign, save the signed PDF, and open it in your PDF reader to see the signature panel.
Frequently asked questions
What do I need to sign?
A certificate file (.pfx or .p12) and its password. Employers, government e-signature services and commercial certificate authorities issue these.
Is the signature legally valid?
PdfForge applies a standard cryptographic PDF signature with your certificate. Whether it is legally recognised depends on the certificate you use and on the rules in your country or organisation, so check with whoever will receive the document.
Why does my reader say the signer is unknown?
The reader does not trust the organisation that issued the certificate — normal for a certificate you created yourself. The signature is still valid and still detects changes; trust is a separate question about who issued the certificate.
What is free and what needs Premium?
Signing is free for documents up to 2 pages, once a day and three times a month, and the free signature is real and valid — not a demo. The one-time Premium upgrade signs documents of any length with no limit.
When should I sign?
Last. Any change after signing — even adding a page or a comment — invalidates the signature, so finish every other edit first.
Get PdfForge free
Compress, merge, split, OCR, sign and redact PDFs entirely on your Windows PC — 50+ tools, nothing uploaded, and a one-time Premium upgrade instead of a subscription.
Download PdfForge — free