Why it matters
A signed PDF is only useful if you can show it is the file that was signed. If someone changes a price, a date or a clause after signing, the signatures on the page still look the same. You cannot spot the difference by eye, and you should not have to.
Every document completed in eSora Sign is sealed so that any later change is detectable. This guide shows three ways to check, from the easiest to the most technical. You can use any of them, and they do not depend on each other.
Method 1: the Verify page
The quickest check is the public Verify page on the eSora Sign website. You do not need an account, and neither does anyone you share the file with.
Open Verify a document and drop the signed PDF onto the page. The file is checked in your browser against our record of the completed document. You can also type the record ID printed on the Certificate of Completion if you only want to look up the record.
If the file matches, the page shows a clear confirmation with the record ID, the completion date and the list of participants. If it does not match, the page tells you the file is not the one we sealed. That does not always mean fraud. The most common causes are innocent: the file was re-saved in another program, printed to PDF, compressed, or someone sent a draft instead of the final copy. Ask for the original download.
Method 2: your PDF reader's signature panel
The tamper seal eSora Sign applies is a digital signature embedded in the PDF itself. PDF readers that support signatures, such as Adobe Acrobat Reader, can show it.
Open the PDF and look for the signature panel. In Acrobat Reader it appears as a bar at the top of the document or as a pen icon in the side panel. Open it and select the seal to see its details.
You will usually see one of three results. Signed and all signatures are valid means the document has not been changed since the seal was applied. Document has been modified since it was signed means someone changed the file after sealing. Validity unknown usually means your reader does not yet trust the certificate that made the seal. It does not by itself mean the document was changed. In that case, the panel often still says the document has not been modified, and you can confirm with Method 1 or Method 3.
The panel also shows the trusted timestamp. A timestamp from an independent time-stamping authority shows that the file existed in this exact form at that moment, which is useful if anyone questions when a document was signed.
Some browser PDF viewers do not show signatures at all. If you see no signature panel, that tells you nothing about the file. Open it in a reader that supports signatures, or use another method.
Method 3: compare the SHA-256 fingerprint
The evidence pack lists a SHA-256 fingerprint of the final signed PDF, and the Verify page shows the same value for a matching record. SHA-256 is a widely used algorithm that turns any file into a 64-character string. If even one byte of the file changes, the string changes completely. Two different files producing the same fingerprint by accident is, for practical purposes, impossible.
You can compute the fingerprint yourself with tools already on your computer.
On Windows, open Command Prompt and run: certutil -hashfile signed.pdf SHA256
On macOS, open Terminal and run: shasum -a 256 signed.pdf
On Linux, run: sha256sum signed.pdf
Compare the result with the fingerprint in the evidence pack. Capital and lowercase letters do not matter. If every character matches, the file is the one that was signed. If anything differs, it is a different file.
There is one subtlety. The Certificate of Completion is a page inside the signed PDF, so it cannot print the fingerprint of the very file it sits in. The fingerprint on the certificate is of the signed document pages before the certificate was added. The fingerprint of the complete file, certificate included, is in the evidence pack's fingerprint list. When you compute a fingerprint of the downloaded PDF, compare it with the evidence pack.
What breaks a seal
Anything that rewrites the file will change its fingerprint and, for most changes, show as modified in the signature panel. That includes obvious edits such as changing text or adding a page, and less obvious ones:
Saving the file again from a PDF editor, even without changes. Printing to PDF or exporting as PDF. Running the file through a compressor or converter. Adding comments or highlights in some readers. Flattening or optimizing the PDF. Printing it and scanning it back in.
If you need to annotate a signed document, make a copy and annotate the copy. Keep the original download untouched.
If a check fails
Do not panic, and do not assume bad faith. Start by asking where the file came from. If it came from your own records, find the original download from eSora Sign. You can always download it again from the completed document, and the Verify page will confirm the fresh copy.
If the file came from another party and does not match, ask them for the original they received when the document was completed. Every participant receives the same sealed file. If the versions genuinely differ, the copy that matches our record is the one that was signed.
For disputes, download the evidence pack. It includes the signed PDF, the certificate, the event log, the original upload, consent records and the fingerprints of every file. That bundle is what a lawyer or court will want to see.
Make checking a habit
For routine documents you will rarely need to verify anything. But for contracts that matter, such as a large sale, a lease or a board resolution, it is worth checking the copy you file away. It takes a few seconds on the Verify page and saves a lot of doubt later.
If you receive signed documents from others regularly, for example in a finance or legal team, consider adding a quick Verify check to your filing process. Agree on one rule: we file the original download, and we check it once before we file it.
This article is general information, not legal advice.