Show that a signed contract hasn't changed since it was signed

Evident, not proof against tampering

Nobody can stop a person from editing a PDF on their own computer. What a tamper-evident record does is make any edit detectable. SignMaster relies on a document hash: a SHA-256 fingerprint, 64 characters long, computed from every byte of a file. Change one character, or even re-save the file, and the fingerprint comes out completely different.

What SignMaster records

• The originalsEach uploaded file's fingerprint is printed on the certificate of completion. Before building the signed copy, SignMaster checks every original against it and stops if one doesn't match.
• The signed PDFThe finished file's fingerprint is shown on the envelope page. It can't be printed inside the PDF itself, because writing it in would change the file.
• Every pageEach page carries the envelope ID and its page number, so a swapped or missing page stands out on sight.
• Flattened fieldsFilled-in values are drawn onto the page rather than left as editable form boxes.
• AttachmentsFiles signers uploaded are listed on the certificate with their own fingerprints.
• The historyThe certificate's event history lists every action with its time and IP address.

Check a copy in a minute

1. 1

   Find the recorded fingerprint

   Open the envelope in SignMaster. Under its documents, the line starting SHA-256 is the signed PDF's fingerprint.

2. 2

   On a Mac

   Open Terminal, type shasum -a 256 followed by a space, drag the PDF into the window and press Return.

3. 3

   On Windows

   Open PowerShell, type Get-FileHash followed by a space, drag the PDF into the window and press Enter. It uses SHA-256 by default.

4. 4

   Compare

   If the two strings match, the file is byte-for-byte the one SignMaster produced. Capital and small letters don't matter; PowerShell prints capitals.

A mismatch doesn't prove fraud. Opening a PDF in some apps and saving it, or printing it to a new PDF, changes the bytes without changing a word. Either way, the copy that matches is the one to rely on, and you can always download it again from the envelope.

What it isn't

SignMaster doesn't apply a certificate-based digital signature to the PDF, so Adobe Acrobat won't show a signature panel for it, and there's no public verification page yet. The evidence is the fingerprint, the page stamps and the certificate. Electronic vs digital signatures explains the difference and when it matters.