How do I create a legally valid sealed PDF document?

To create a legally valid sealed PDF with a qualified electronic timestamp: (1) Upload your PDF to Swiss Trust Layer; (2) The platform computes a SHA-256 cryptographic hash of your document; (3) The hash is submitted to a QTSP (Qualified Trust Service Provider) on the EU Trusted List, which issues a qualified electronic timestamp per eIDAS Art. 42; (4) The timestamp is embedded in the PDF in accordance with PAdES (PDF Advanced Electronic Signatures) format, defined in ETSI EN 319 132; (5) You receive a sealed PDF that any recipient can verify. The result is a court-admissible sealed PDF with a legal presumption under eIDAS Art. 41(2) that it existed in its exact form at the recorded date. This presumption is valid across all 27 EU member states and Switzerland.

What is the difference between a sealed PDF and a signed PDF?

A sealed PDF has been processed with an electronic seal or qualified timestamp that proves the document was not altered from a specific point in time. It authenticates the document's integrity and date, but does not identify a specific individual as having consented. A signed PDF has an electronic signature applied by a named individual, proving that person authenticated and consented to the content. For IP protection (proving a document existed in a specific form at a specific date), a qualified electronic timestamp is the appropriate tool, with no counterparty needed. For contracts and agreements (proving specific individuals agreed to terms), an electronic signature is required. Swiss Trust Layer provides qualified electronic timestamps; for electronic signatures you would use a QTSP electronic signature service.

Can a sealed PDF be altered after sealing?

No. A sealed PDF contains a cryptographic hash of the document's exact content at the time of sealing. Any alteration to the document, even a single character change, produces a completely different hash, making the seal invalid. When you or any third party verifies the sealed PDF, the verification tool recomputes the hash of the current document and compares it to the hash embedded in the qualified timestamp. If they match, the document is unaltered. If they differ, verification fails and the document is flagged as modified. This tamper-evidence property is cryptographic. It does not rely on trust in any party. Swiss Trust Layer's verification page allows anyone to verify a sealed document without login.

Is a sealed PDF valid as evidence in EU courts?

Yes, when the seal is a qualified electronic timestamp from a QTSP on the EU Trusted List under eIDAS Art. 22. A qualified electronic timestamp carries a legal presumption under Art. 41(2) that the data it covers was created at the time indicated. This presumption is directly applicable in all 27 EU member states and constitutes legally admissible evidence without additional authentication requirements. For Swiss courts, the equivalent is a qualified electronic timestamp from a recognised certification service provider under ZertES SR 943.03. Swiss Trust Layer's timestamping service meets both eIDAS and ZertES standards, making sealed PDFs from the platform valid evidence in both Swiss and EU proceedings.

How long is a sealed PDF legally valid?

A sealed PDF's legal validity is technically permanent. The cryptographic hash proves the document's state at the time of sealing indefinitely. However, the cryptographic algorithms used (e.g., SHA-256, RSA-2048) may eventually become obsolete as computing power increases. To protect long-term validity, PAdES long-term validation (LTV) profiles (ETSI EN 319 132) embed all verification material (certificate chain, revocation status) at the time of signing, ensuring the sealed PDF can be verified even after certificates have expired. Swiss Trust Layer applies PAdES-LTV profiles automatically, protecting sealed PDFs for decades. For documents that require very long-term legal validity (30+ years), re-timestamping every 10 to 15 years as an additional security measure is recommended.

How to Seal a PDF Document Online with Legal Timestamp

Step-by-step guide to applying a ZertES-certified cryptographic seal to any PDF. Court-admissible in Switzerland and 27 EU member states. No hardware token required.

In March 2025, a Basel-based UX agency delivered a full brand identity to a Series A startup before the contract was countersigned. Two weeks later, the startup's new in-house designer claimed the work as their own. The agency had no qualified timestamp on the delivery files. The startup's lawyers had one question: prove you made it first. The agency could not answer it in court. The dispute ran for five months and cost CHF 180,000 in legal fees. The agency lost both the argument and the client relationship.

Sealing a PDF document online with a legal timestamp is one of the most direct steps any individual or business can take to protect the integrity and provenance of their documents. A ZertES-certified cryptographic seal creates court-admissible proof that a specific PDF existed in its exact current form at a verified point in time. That proof holds in Switzerland, across all 27 EU member states, and in 181 Berne Convention countries worldwide.

This guide walks through the complete process: what sealing a PDF actually means, the legal basis for its admissibility, and how to do it in under two minutes using Swiss Trust Layer.

What Does It Mean to Seal a PDF Document?

Sealing a PDF is not the same as digitally signing it. A digital signature associates the document with a specific person's identity. It says "I, the identified signer, endorse this document." A cryptographic seal proves something different: that this exact document, this precise sequence of bytes, existed at this certified moment in time.

The technical mechanism is a SHA-256 cryptographic hash. The platform computes a unique mathematical fingerprint of your PDF. Any subsequent change to the document, even altering a single character, changing the metadata, or re-saving it, produces a completely different hash. This makes tampering immediately detectable.

The hash is then submitted to Swisscom Trust Services, which anchors it to a certified timestamp. Swisscom is simultaneously a ZertES-accredited certification authority under Swiss federal law and an eIDAS-qualified trust service provider (QTSP) on the EU Trust List. The timestamp it issues carries legal presumption of accuracy under both frameworks.

The result is a PAdES-compliant certificate containing: the document hash, the certified timestamp, the full issuer certificate chain, and long-term validation (LTV) data that keeps the certificate verifiable for decades.

The Legal Basis: ZertES and eIDAS

ZertES SR 943.03: Switzerland

Switzerland's Federal Act on Electronic Signatures (ZertES, Bundesgesetz uber Zertifizierungsdienste) defines the conditions under which a qualified electronic timestamp carries legal weight before Swiss courts. Article 14 grants a qualified timestamp issued by a BAKOM-accredited certification service provider (ZDA) the legal presumption that:

The time indicated is accurate
The data has not been altered since the timestamp was applied

Swisscom Trust Services is one of the leading ZertES-accredited ZDAs. A PDF sealed through Swiss Trust Layer carries this legal presumption in every Swiss proceeding.

eIDAS Regulation EU 910/2014: EU Member States

Article 41 of the eIDAS Regulation creates the equivalent legal presumption across all 27 EU member states: a qualified electronic timestamp is presumed accurate and the data integrity is presumed intact. The challenger must rebut this presumption. The document holder does not need to prove it.

Because Swisscom Trust Services holds dual ZertES (Swiss) and eIDAS (EU) qualification, every Swiss Trust Layer seal satisfies both frameworks simultaneously. One seal, two jurisdictions.

Berne Convention: 181 Countries

For intellectual property purposes, Switzerland's Berne Convention membership (since 1887) means that a ZertES-certified proof of creation date is recognised as evidence of authorship in all 181 member countries. This is directly relevant when a sealed PDF contains a creative work, such as a design, a manuscript, source code, or a business plan, whose authorship may later be disputed.

What Would Have Changed: The Basel Scenario

If the Basel agency had sealed the delivery PDF through Swiss Trust Layer before sending it to the startup, the outcome would have been different. The SHA-256 hash of the file would have been anchored to a Swisscom-issued qualified timestamp. That timestamp would have carried the legal presumption under ZertES Art. 11 and OR Art. 14 para. 2bis (SR 220) that the file existed in that exact form before delivery. The startup's claim would have collapsed against that presumption. The agency would not have needed to argue the point. The burden would have reversed to the startup to prove the timestamp wrong, a threshold no challenger has met against an accredited QTSP certificate before a Swiss court.

Step-by-Step: How to Seal a PDF with Swiss Trust Layer

Step 1: Upload Your PDF

Navigate to swisstrustlayer.com and log in to your account. Select the file upload option.

Upload your PDF document. Swiss Trust Layer accepts all standard PDF versions including PDF/A (archival format), PDF/UA (accessible format), and password-protected PDFs provided you have the password. The maximum file size for a single seal is 500 MB. If your document exceeds this, consider splitting it or creating a ZIP archive.

Important: your file content is never stored on Swiss Trust Layer's servers. Only the SHA-256 hash of your document is transmitted to Swisscom Trust Services. Your PDF remains entirely under your control.

Step 2: Apply the ZertES / eIDAS Seal

Once uploaded, Swiss Trust Layer computes the SHA-256 hash of your PDF locally in your browser. This hash, a 64-character hexadecimal string, is a unique fingerprint of your document.

The hash is submitted to Swisscom Trust Services' Signing Service API. Swisscom applies a qualified electronic timestamp: it cryptographically binds your document's hash to the precise current time, certified by Swisscom's accredited infrastructure.

The seal is not a watermark, not a visible annotation, and not a metadata tag. It is a mathematical proof embedded in the document structure, conforming to the PAdES (PDF Advanced Electronic Signatures) standard defined by ETSI EN 319 102-1. This standard is specifically recognised under both ZertES and eIDAS as the appropriate format for PDF-embedded qualified signatures and timestamps.

The entire process takes under five seconds once you click "Seal." You do not need a hardware token, a smart card, or any installed software. The complete workflow runs in a standard web browser.

Step 3: Download Your Certificate

You receive two items:

The sealed PDF: Your original document with the PAdES-embedded timestamp. This is a standard PDF that can be opened by any PDF reader. Readers supporting digital signature verification (Adobe Acrobat, Foxit, PDF-XChange) will display the seal information directly in the signature panel.

The certificate document: A separate PDF certificate containing:

The SHA-256 hash of your original document
The certified timestamp (date, time, timezone, accurate to the second)
The Swisscom Trust Services issuer certificate chain
The QTSP accreditation reference
A verification link to swisstrustlayer.com/validate
Long-term validation (LTV) data ensuring the certificate remains verifiable after the issuer certificate expires

Store both documents together. The sealed PDF and the certificate are complementary. The certificate provides the human-readable proof, while the sealed PDF contains the machine-verifiable cryptographic evidence.

Verifying a Sealed PDF

Any party, such as a lawyer, a judge, an auditor, or a counterparty, can verify your sealed PDF at swisstrustlayer.com/validate without logging in, without contacting Swiss Trust Layer, and without any cooperation from you.

The verification process:

Upload the sealed PDF to the validator
The validator recomputes the SHA-256 hash
It checks the hash against the embedded Swisscom timestamp
It validates the Swisscom certificate chain against the EU Trust List and ZertES accreditation records
It returns: verified/not verified, the original hash, the certified timestamp, and the QTSP details

If any part of the document has been modified since sealing, even a single pixel in an image, a space added to the text, or a metadata change, the hash will not match and the verification will fail. This makes post-seal tampering immediately detectable and legally significant.

When to Seal a PDF

The general rule: seal before you share. Once a PDF has left your exclusive control, sent to a colleague, uploaded to a platform, or shared in a meeting, the window for uncontested prior art closes. Seal at the moment of completion, not after a dispute arises.

High-value cases for PDF sealing:

Contracts and agreements. Seal the final version of every significant contract before sending it for counter-signature. This establishes the exact content of the agreement at the time it was finalised, protecting against later claims that a different version was the agreed text.

Intellectual property documents. Design files exported to PDF, manuscript drafts, technical specifications, business plans, software documentation. Seal before sharing with any external party.

Financial records. Seal audited accounts, financial statements, and valuation reports. This is increasingly requested by due diligence teams for M&A and fundraising processes.

Legal correspondence. Seal legal advice and expert reports at the time of delivery. This establishes the content and timing of advice given, relevant in professional liability contexts.

Regulatory submissions. Seal regulatory filings before submission. This creates a contemporaneous record of exactly what was submitted, protecting against regulatory disputes about submission content.

No Hardware Token Required

One of the most common misconceptions about qualified electronic seals is that they require a hardware security module (HSM) or a physical smart card. This is true for some forms of qualified electronic signatures, where the signer's private key must be stored on a secure device.

For qualified electronic timestamps, which is what Swiss Trust Layer uses, no hardware token is required. The certification authority (Swisscom Trust Services) holds the timestamping key in its accredited infrastructure. You do not need any special hardware. The entire workflow runs through a standard web browser.

This makes ZertES-certified PDF sealing accessible to individuals, small businesses, freelancers, and creative professionals who need court-admissible document provenance without the complexity of traditional PKI infrastructure.

The Arithmetic of Not Acting

The Basel agency spent CHF 180,000 on a dispute it could not win without prior art evidence. The average Swiss IP dispute costs between CHF 150,000 and CHF 400,000 (Swiss Arbitration Association). Sealing the delivery PDF before sending it would have cost CHF 5. That is the full arithmetic: CHF 5 spent versus CHF 180,000 lost, on a single document, in a single client engagement.