What is Tamper-Evident?

A property where any post-signing change to a document is immediately detectable through a hash mismatch.

A tamper-evident signed document carries a cryptographic seal, a hash of the document at signing time, that lets anyone verify whether the document has been altered since. Open the signed PDF, recompute the SHA-256, compare against the hash on the audit certificate; if they match, the document is untouched. If they don't, even a single byte has changed. PDF Verified publishes the hash on the audit certificate and on the public /verify QR page so verification is one click away.

Drop your document here and sign it now. PDF, Word and Excel all work: a .docx or .xlsx is laid out in your browser exactly as it was written, so there is nothing to convert first. Add a signature, a date, a company stamp or a watermark, then download it sealed. Free to start, no account, and the file is never uploaded to open it.

Tamper-evident vs tamper-proof

No digital document is truly tamper-proof, anyone can edit a PDF in Acrobat. But tamper-evidence means the change is immediately visible: the hash on the audit certificate no longer matches the live document. Tampering becomes self-defeating.

PKI seals

A stronger form: the signed PDF carries an embedded PKI signature (an Adobe-recognized digital signature). Adobe Reader will display a yellow or red banner the moment any byte changes. PDF Verified adds embedded PKI seals on Business Plus.

In court

In ESIGN/eIDAS jurisdictions, a tamper-evident hash on a contemporaneous audit certificate is admissible evidence of document integrity. Combined with the audit trail, it answers the two questions a court asks: who signed, and has anything changed since.

What PDF Verified is, and what it is not

These checks are a screen, not a verdict. A clean result means nothing was found by the checks that were run, which is not the same as proof that a document is genuine, and a flagged result can have an innocent explanation such as a re-save or a scan. Read the findings rather than the headline, and where a decision carries real consequences, confirm the document with the party that issued it. It is a tool for examining a document, not for producing a forged or altered one.

PDF Verified is a tool for preparing, signing, stamping and checking documents. It is not a law firm, a compliance service or a forensic examiner, and nothing here is legal, financial or compliance advice. Requirements differ by country, by document type and by the party asking, so check what applies to your document before you rely on it, and take advice where the document matters. You are responsible for the documents you create, sign and send, and for having the authority to do so: signing or stamping in somebody else name, or as an organisation you do not represent, is forgery whatever tool is used. To the extent the law allows, we accept no liability for how a document made with this tool is used or relied on. The full position is in our terms of service.