What is a Certificate of Execution on a signed PDF?
It is a page added to the signed copy that names the exact source file by its SHA-256 hash, lists every signature and stamp placed with coordinates and time, and hashes that list. It shows what was signed and when — it is not a trusted timestamp.
What is on the page
The source file's SHA-256, the page count, and a manifest of each stamp: what it was, where it went, and the device time it was placed. Then a hash over the manifest itself.
The same manifest is written into the PDF's Subject metadata, so a checker can compare the two without reading the page.
What it proves
If the recipient holds the original contract, they can compute its SHA-256 and compare. A match proves the signed copy came from that exact document — not a version with a changed date or a swapped exhibit.
The manifest hash can be recomputed from the values printed on the page. Any edit to a name, a coordinate or a time breaks the match, which is the point.
What it cannot prove
No trusted timestamp. There is no timestamp authority, so the clock is the signing device's, and the page says so rather than implying otherwise.
No protection against later edits. Someone who alters the signed file after export leaves the certificate untouched; the mismatch only appears when the original is compared. Stopping that needs a third-party key or a public log, both of which need a server — and needing no server is why the document never leaves the tab.
It cannot contain the hash of the signed file itself. Hashing a string that contains its own hash is circular, so the certificate records the source hash instead.
How to check one
Run the source file through the verifier, and read the values off the certificate page. The verifier recomputes the manifest hash and compares it to the printed value and to the PDF metadata.
A match means the certificate is internally consistent and belongs to that source. A mismatch means something was changed — start with the file you were given.
Is this the same as a digital signature?
No. A digital signature uses a private key and a certificate authority. This is a recorded hash and a manifest, which is evidence rather than cryptography.
Does every signed PDF need one?
No. It matters when the recipient needs to check what was signed — an exhibit-heavy contract, a tender, a document that will be disputed. For an internal form it is noise.
Can the certificate itself be forged?
Anyone can write a page that looks like one. It becomes meaningful only when the recipient compares the source hash to their own copy of the original, which a forger cannot match.
This page is general information, not advice for your document. The tools do what they say on their own pages, and every limit is printed there.