PDFMaxSign PDF with a Digital Certificate
Need to digitally sign a PDF with your own certificate? This free tool lets you apply a certificate-based digital signature using a PEM or P12 (PFX) file, right in your browser. Unlike a drawn signature, a certificate signature cryptographically binds your identity to the document and flags any later changes. Upload your PDF, add your certificate and password, and download a signed file in seconds. There is no signup, no software to install, and nothing to learn. It works the same on phones, tablets, and computers, so you can sign a document wherever you are.
Sign PDF with Certificate →100% freeNo signupWorks in your browser
Why PDFMax
- Use your own PEM or P12 (PFX) certificate to apply a real, certificate-based digital signature, not just a drawn image.
- Completely free with no signup and no software to install — everything runs in your browser.
- Tamper-evident result: the signature is tied to the document, so any later edit breaks it and is easy to spot.
- Works on mobile and desktop in any modern browser, with the original PDF layout and quality preserved.
How to sign PDF with certificate
- Upload your PDFOpen the cert-sign tool and select the PDF file you want to sign from your device.
- Add your certificateUpload your certificate in PEM or P12 (PFX) format and enter its password if the file is protected.
- Apply the signatureConfirm the details and let the tool embed a certificate-based digital signature into the document.
- Download the signed PDFSave the signed file to your device. Anyone can verify the signature in a standard PDF reader.
Frequently asked questions
Is it free to sign a PDF with a certificate?
Yes. The tool is completely free with no signup, no subscription, and no software to install. Just upload your PDF and certificate and download the signed file.
Is it safe and private?
Your files and certificate are used only to create the signature and are not kept afterward. Because you supply your own PEM or P12 file, your private key stays under your control.
What certificate formats are supported?
You can use a PEM certificate or a P12/PFX file. If your certificate file is password-protected, enter the password so the tool can sign with it.
Are there any limits?
There is no signup and no account needed. The tool is meant for everyday documents and runs in your browser, so very large files depend mainly on your device and connection.
Does it work on a phone?
Yes. The signer runs in any modern mobile or desktop browser, so you can sign a PDF on a phone, tablet, or computer without installing an app.
Will signing change the quality of my PDF?
No. The tool adds a digital signature without re-rendering your pages, so the original text, layout, and image quality stay exactly the same.