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Add legally binding digital signatures to PDFs to ensure document authenticity and integrity.
Choose filesUpload PDF File
PDF (Supported formats: .pdf)
Max 2.5 MB
If your type isn't listed, convert to JKS using keytool
Enter password if applicable
Upload files and configure options, then click start processing
Overview
Understand what the tool solves, how it works, and the boundaries of its data.
This tool applies a certificate-based digital signature to one PDF and returns a signed PDF. This is different from typing a name, drawing a signature, or placing an image on a page: a digital signature is cryptographic data associated with the document and a signing key. A PDF reader that supports signature validation can use it to check whether the signed document data has changed and inspect certificate information.
NIST’s Digital Signature Standard describes digital signatures as a way to detect unauthorized data changes and authenticate a signatory. A successful cryptographic check is only one part of validation: identity assurance, certificate trust, and the recipient’s rules also matter. PDF itself is standardized by ISO 32000-2:2020, which ISO reviewed and confirmed as current in 2026. These standards describe the format and technical purpose; they do not mean every recipient will accept every signed file.
Choose a PDF no larger than 2.5 MiB. Select a certificate type—PEM, PKCS12, or JKS—and provide the corresponding private-key or keystore file. Accepted filename extensions include .pem, .der, .p12, .pfx, .jks, and .key. PKCS12 files are commonly encountered as .p12 or .pfx bundles. The selected type must match the material you supply; an extension alone does not establish that a file is a valid certificate and private key.
If the private key or keystore is password-protected, enter its password. Optional fields let you set a reason, location, and name. You can also request a visible signature mark, choose its page number (starting at 1), and choose whether to show a logo. The visible mark is a page appearance; the cryptographic signature is separate and can exist without a visible mark.
Guide
Follow the workflow and verify inputs and outputs with practical examples.
Upload the document you intend to sign. The input limit is 2.5 MiB. Keep an unchanged copy so you can compare the returned file and retain your original.
Select PEM, PKCS12, or JKS, then choose the related private-key or keystore file. If the file is protected, enter its password in the password field. Do not put a password in the reason, location, or name fields.
Add reason, location, or name only when those details are appropriate for your workflow. Turn on the visible signature option if you want a mark on the page; set the page number and logo option to suit the document.
Run the signing action and download the resulting PDF. Open it in a PDF reader that supports digital signatures. Review the signature panel or validation details, the certificate information, any document-change notice, and the visible mark if enabled.
Use cases
See how the tool fits into real work and everyday tasks.
A team member with an authorized signing key can add a cryptographic signature to a finalized approval PDF. The recipient can inspect the signature information in a compatible reader as part of the organization’s own review process.
When a counterparty asks for a certificate-signed PDF, prepare the final file, apply the signature, then check that the recipient accepts the certificate type and validation method before relying on the copy.
If readers need to notice that a document was signed, enable the visible mark and select a page. Treat this as a visual aid; anyone reviewing authenticity should still validate the embedded signature data.
Q&A
Find concise answers to common questions and confusing cases.
No. The mark is a visual page element. A digital signature is validated from the signature data and certificate in a compatible PDF reader, whether or not a mark is displayed.
Check that the selected type matches the file, that the file contains the signing key material required for signing, and that you entered the matching keystore or private-key password. A certificate without its corresponding private key cannot create a signature.
Not necessarily. Readers may differ in certificate trust settings and validation support. Check the recipient’s requested reader or validation process, and review any warning instead of treating a signature icon alone as conclusive.
A signature does not make a PDF physically impossible to edit. Changes may cause validation warnings or affect the signature status; permitted changes depend on the signature and document rules. Recheck the signed file after any later change.
Notes
Review scope, result limitations, and important precautions before use.
The PDF, key file, and any entered password are sent away from your device for online processing. A private key can be used to make signatures associated with its certificate, so only provide key material you are authorized to use and only when your organization permits this handling. For sensitive files or keys, use an approved signing environment.
This tool creates an output file; it does not establish who controlled the key, validate a certificate trust chain for a recipient, confirm that a certificate is current or authorized, or decide whether a signature meets a contract, agency, court, or other recipient’s requirements. Legal effect and acceptance depend on applicable law, the facts, the certificate and signing process, and the recipient’s rules. Confirm those requirements separately before relying on a signed PDF.
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