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Mofumi PDF

Digital Signature (Certificate)

Sign a PDF cryptographically with your .p12 / .pfx certificate so any change after signing is detected.

100% Private — files never leave your device
Upload PDFDrop files here or click to chooseAccepted: PDF Files never leave your device

About this tool

Digital Signature adds a real cryptographic signature (PAdES basic, adbe.pkcs7.detached with SHA-256) using your own certificate file (.p12 or .pfx). Adobe Acrobat and other readers show who signed the document and when, and flag the signature as broken if even one byte is changed afterwards.

You can add a visible signature box with the signer’s name, date, reason and location on the first or last page, or sign invisibly. The certificate and its password are used only in your browser’s memory for this one signature and are never uploaded or saved.

Readers trust the signer’s identity only if the certificate comes from an authority they know (for example a certificate from a Thai CA approved by ETDA) or if the recipient trusts your certificate manually. Self-signed certificates still protect integrity but show an “unknown identity” warning.

Engines: forge · pdf-lib · fontkit

How to use

  1. 1

    Upload the PDF and choose your .p12 / .pfx certificate file.

  2. 2

    Enter the certificate password and, optionally, the reason, location and box position.

  3. 3

    Click Sign with certificate and download the signed PDF.

Use cases

  • e-Contracts and quotations

    Sign agreements so the other side can verify they were not changed.

  • Official documents

    Sign reports, certificates or e-tax documents with your organisation’s certificate.

  • Approvals

    Add a verifiable approval signature to internal requests and invoices.

Frequently asked questions

Is this the same as drawing my signature?

No. Sign PDF places a picture of your handwriting; this tool adds a cryptographic signature that proves integrity and identity.

Is my certificate uploaded?

No. The certificate and password stay in your browser’s memory and are discarded after signing.

Which certificates are supported?

RSA certificates in .p12 / .pfx files. Elliptic-curve (ECDSA) keys are not supported yet.

Can I edit the PDF after signing?

Any change invalidates the signature, so make signing the last step.

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