Check what a signed PDF says about itself PDFSIG
Checks in this tab whether anybody changed a PDF after it was signed: it hashes the bytes the signature covers, compares that with the digest in the signature, and shows every byte it leaves out.
1. The signed PDF
Any PDF. If it has no signature, it says so.
2. What the signature says, and what the bytes say
The first is a claim. The second is arithmetic. They are kept apart below.
How it works
PDFSIG checks whether that happened: it hashes the bytes the signature covers, compares them with the digest stored in the signature, and shows whether anything was added afterwards and what changes the signer allowed. A matching digest means the signed bytes are intact. It does not by itself prove who the signer really was. Your PDF is not uploaded.
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