Verify

Check a signed document

Drop in a PDF that was signed through Pixasign and we will tell you whether a single byte has changed since it was sealed. You do not need an account, and the file is not stored. It is checked and discarded.

Choose a signed PDFThe file is checked and dropped. Nothing is kept.

Why Adobe Reader shows a warning

Open a Pixasign document in Adobe Reader and you will see a notice saying the validity of the signature is unknown. That is not a fault, and it does not mean the document has been altered. Adobe is telling you it has not been asked to trust Pixacomms Ltd in advance: membership of its trust list costs several thousand pounds a year and we have not bought it.

The cryptography is unaffected. The seal still proves the file has not changed by one byte since signing, and the timestamp still comes from DigiCert, whose root Adobe does trust. This page checks all of it properly.

What we check

That the document carries a Pixasign seal at all.
That the seal is intact, so not one byte of the document has changed since it was signed.
That the seal was made by us, and not by somebody who created their own signature field with a similar name.
That the signature covers the whole file. This is the one that catches a page appended after the fact.
That the timestamp comes from a real, trusted authority.