Signzuma
Check a signed document
Every document signed with Signzuma has a fingerprint (SHA-256) recorded when the last person signs. Drop a copy here to see whether it is that document, unchanged. Your browser works out the fingerprint; the file is not uploaded.
The digital seal
Signed documents also carry a digital signature applied when they are completed. Open the file in Adobe Acrobat Reader and look at the Signature Panel: it says whether the document has been modified since it was sealed. Because the seal uses Filezuma’s own certificate rather than one from Adobe’s trust list, Acrobat may describe the signer’s identity as unknown; the check that nothing changed works either way.
To trust the seal in Acrobat, download Signzuma’s public certificate and add it under Preferences → Signatures → Identities & Trusted Certificates.