Green checkmark in Adobe Acrobat

A qualified electronic timestamp (QTS) is an electronic timestamp issued by a Qualified Trust Service Provider (QTSP) listed on the EU Trusted List. Under eIDAS Article 41, it enjoys the legal presumption of accuracy of the date and time it indicates.

When a PDF contains a valid qualified timestamp, Adobe Acrobat shows a green checkmark in the signature panel. This indicates that the document has not been modified since the timestamp was applied and that the timestamp comes from a trusted source.

Acrobat and Reader ship with the European Union Trusted Lists (EUTL), a consolidated list of all qualified trust services in the EU and EEA. Our timestamp authority is on that list, so no manual configuration is needed. Acrobat refreshes the lists roughly every 30 days.

A PAdES DocTimeStamp is appended as an incremental update: the original bytes are left untouched and the timestamp is written after them. The token contains the hash of the document, the time from the TSA and the TSA certificate chain. No visible stamp is drawn on the pages.

No. A timestamp proves when a document existed and that it has not changed since; a signature proves who signed it. A timestamp needs no certificate of your own and no identity check. The two can be combined: sign first, then timestamp.

No. The timestamp is embedded on our own server, and only the SHA-256 hash of the document is sent to the timestamp authority. That hash cannot be turned back into the document, so the TSA never learns what it stamped.

Yes. Because the timestamp is added as an incremental update, existing digital signatures remain valid. Any timestamps already present are kept as well — you can see the total count in the result.

We use Disig a.s., a Qualified Trust Service Provider (QTSP) from Slovakia, listed on the EU Trusted List. The timestamps are RFC 3161 compliant and embedded as PAdES DocTimeStamp signatures.

Two causes account for almost every failure: the PDF is encrypted or permission-restricted (remove the password first), or it exceeds the size limit. A damaged PDF that Acrobat itself cannot open properly will also be refused.

A qualified timestamp costs 20 credits per document. You need a paid account for it — either a onetime credit bundle or a premium subscription will do. Free accounts cannot place timestamps.

Currently you can timestamp one PDF at a time. Upload your document, download the stamped version, and repeat for additional files.

A fingerprint compares two versions of a document and shows where they differ: the bytes, the text, the rendering or the metadata. That comparison says nothing about time by itself. A timestamp does the opposite — it dates the document but compares nothing. If you need to show that a version you received differs from yours, you need the fingerprint; if you need to show that your version came first, the timestamp.

Both rely on a qualified European timestamping authority, so that is not where they differ. The difference is form and timing. The proof package is a separate ZIP alongside your document: the recipient has to keep it and open it to verify anything, and anchoring happens in a daily run. A qualified timestamp is placed immediately and sits inside the PDF, where Acrobat shows a green check mark for it without anyone needing an attachment. It also works on any PDF you upload, including a document that was not created here.

Yes, but mind the order. The timestamp is appended to the PDF as an incremental update, so afterwards the file is no longer byte-identical to the version anchored during conversion. Both proofs stay valid, but they then cover two versions of the same document. If you want one file carrying both, timestamp as the last step and keep exactly that copy.