What is the difference between an ADOC file and a signed PDF?

A signed PDF embeds the signature inside the document itself, so the file stays an ordinary PDF that opens anywhere. An ADOC file is a container: a ZIP package holding the original document, structured metadata and detached XAdES signature files. That makes ADOC flexible — it can carry any supported content type, attachments and multiple signatures — but it needs software that understands the format. In Lithuania's public sector ADOC is the standard; for commercial and cross-border contracts a signed PDF is usually the more practical choice, because every counterparty can open it without special tools.

Is a document signed in ADOC format legally valid?

The container does not decide legal validity — the signature inside it does. Under eIDAS, an electronic signature cannot be denied legal effect merely because it is electronic, and a qualified electronic signature has the same legal effect as a handwritten one across the EU. ADOC documents signed with Lithuanian eID means normally carry qualified signatures, which is why institutions accept them. Whether a specific document meets the form requirements of a specific transaction depends on the law that applies to it — see our overview of when e-signatures are legally binding in the EU. This is general information, not legal advice.

Can I open an .adoc file without special software?

Partly. ADOC is a ZIP package, so renaming document.adoc to document.zip lets any archive tool show the contents — the main document, attachments and signature XML files. That is enough to read the document, but it verifies nothing: you cannot tell whether the signatures are valid or the content untampered. For actual verification, upload the file to the free state tool at adoc.archyvai.lt or to another service that validates ADOC signatures, and keep the original file unchanged — repackaging the ZIP by hand can break the container's integrity.

What should I do if my counterparty cannot open an ADOC file?

This happens often outside Lithuania, where ADOC tooling is largely unknown. If the document is not yet signed and no institution requires ADOC, the simplest fix is to sign a PDF instead — it opens everywhere and supports embedded signatures. If the ADOC already exists, send your counterparty the file together with a link to the free verification tool at adoc.archyvai.lt. What you should not do is print, scan or convert the signed document: the result loses the electronic signatures entirely and has to be treated as a mere copy.

How do I check who signed an ADOC document and when?

Upload the file to the state verification tool at adoc.archyvai.lt or to Lithuania's e-government portal epaslaugos.lt. The verification report lists each signer, the data from their certificate, the time of signing, any timestamps, and whether each signature is valid and at what level. If the report flags a problem — an expired certificate at signing time, altered content, a broken signature — do not rely on the document and ask the sender for a properly signed version. For contracts, keep the verification result together with the original file as part of your evidence.

Signing · How-to

What Is an ADOC File? How to Open, Sign and Verify Lithuania's National Document Format

Edvinas B.Jul 3, 20268 min read

Laptop on an office desk displaying a document opened for review before electronic signing, with printed papers beside it

If a Lithuanian institution has ever sent you a file ending in .adoc, you have met Lithuania's national format for electronically signed documents. An ADOC file is not a strange kind of PDF — it is a signed container: a ZIP package that holds the document itself, its metadata and one or more XAdES electronic signatures, all structured according to the official ADOC-V1.0 specification approved by the Lithuanian Chief Archivist.

This guide explains what the ADOC format is, how it differs from signed PDFs and the EU-standard ASiC-E container, how to open and verify an .adoc file with the official state tools, and how to sign one yourself. We also answer the practical question behind it all: when you will get ADOC and when PDF — and how modern contract workflows deal with both.

Key takeaways

ADOC is Lithuania's national signed-document format, defined by the ADOC-V1.0 specification of the Lithuanian Chief Archivist and used for official electronic documents.
An .adoc file is a ZIP container holding the document, its metadata and detached XAdES signatures — it is not a special kind of PDF.
Open and verify ADOC files free of charge with the state tool at adoc.archyvai.lt (rebuilt in January 2026); renaming the file to .zip shows the contents but verifies nothing.
ADOC vs PDF: Lithuanian institutions default to ADOC; for commercial and cross-border contracts a signed PDF is usually the more practical choice.
ADOC is conceptually close to the EU ASiC-E container; Estonia (.asice) and Latvia (.edoc) use their own national equivalents.
The signature level (SES, AES or QES) — not the container — determines legal weight; match it to the risk of the document.

What is an ADOC file?

ADOC is Lithuania's national format for electronically signed documents. It is defined by the specification ADOC-V1.0, approved back in 2009 by the head of the then Lithuanian Archives Department and maintained today by the Office of the Chief Archivist of Lithuania (Lietuvos vyriausiojo archyvaro tarnyba). The specification describes how an official electronic document must be packaged, what metadata it must carry and how its signatures must be formed, so that state and municipal institutions can exchange, verify and archive documents in one predictable way. Lithuanian institutions are required by the Chief Archivist's orders to accept official electronic documents prepared to this specification, which is why the format is everywhere in the public sector. The file extension is .adoc, and the format even has its own registered media type: application/vnd.lt.archyvai.adoc-2008.

Technically, an .adoc file is a ZIP container. Inside you will find the main document (typically a PDF, an OpenDocument or OOXML file such as .docx, or an image format like JPEG or TIFF), any attachments, structured metadata (title, registration details, the signer's role, the purpose of signing) and one or more electronic signatures in the XAdES XML format. Each signature is stored as a separate, detached file inside the package, so a single ADOC document can carry multiple signatures — useful when a document needs a manager's signature plus a registrar's confirmation, or several parties. The specification allows signature forms from basic XAdES up to archival forms with timestamps and long-term validation data.

You will meet ADOC files wherever the Lithuanian public sector is involved: official letters and certificates issued by state or municipal bodies, documents submitted through e-government portals, and records destined for long-term storage in the state archives. Businesses usually encounter the format as recipients — an institution answers a request with an .adoc file — or when a specific procedure requires documents to be submitted in ADOC. In purely commercial, business-to-business contracting, by contrast, the format is rare: there the signed PDF dominates, because any counterparty in any country can at least open it. That split — public sector on ADOC, business on PDF — is the single most useful thing to remember about the format.

ADOC vs signed PDF vs ASiC-E: what is the difference?

A signed PDF (the eIDAS-friendly flavour is the PAdES standard) embeds the signature inside the PDF file itself. The document stays a normal PDF: anyone can open it in any reader, and capable readers or validation services can check the signature. Nothing about the file name changes, and the visible document and the signed object are one and the same file. This is why PDF is the default for commercial contracts across the EU — the file travels well, and the signature travels with it.

ADOC takes the opposite approach: instead of embedding the signature in the document, it wraps the document — unchanged — in a container together with detached signature files and metadata. The benefit is flexibility: you can sign any supported content type, attach related files and record rich, signable metadata. The cost is tooling: a generic PDF reader or file manager cannot validate an ADOC signature, so the recipient needs software that understands the format. Conceptually, ADOC is close to ASiC-E, the EU-standardised signature container defined by ETSI: both are ZIP packages carrying XAdES signatures. Estonia's .asice/.bdoc files and Latvia's .edoc are the neighbouring national equivalents — each Baltic state standardised its own container before and alongside the common EU rules.

Inside the Lithuanian public sector, ADOC is the default and in many procedures the required format. The Chief Archivist also approved a national specification for signed PDFs (PDF-LT-V1.0, in 2014), but institutions were never obliged to use it, so it never displaced ADOC in practice. Outside the public sector the calculus flips: for cross-border and commercial work, a signed PDF or an ASiC-E container is far easier for counterparties to consume. Neither choice changes the legal nature of the signature inside — a qualified electronic signature is qualified whether it lives in an ADOC container or in a PDF. The container is packaging; the signature level is what carries legal weight.

How to open and verify an .adoc file

The simplest way to open an ADOC document is the official state tool at adoc.archyvai.lt, run by the Office of the Chief Archivist. It is free and browser-based: upload the .adoc file and you can view the main document and attachments, see the metadata and check every signature. The tool was rebuilt in January 2026 — the updated version works across modern browsers and operating systems and added support for signatures based on elliptic-curve cryptography. ADOC documents can also be created and verified through Lithuania's e-government portal epaslaugos.lt, and several commercial e-signing platforms operating in Lithuania open and validate the format as well.

Verification is more than opening the file. A proper ADOC check confirms four things: that the content is intact (nothing in the package changed after signing), that each signer's certificate was valid at the moment of signing, that any timestamps hold up, and what level each signature actually is — qualified or not. The state tool reports all of this per signature. Treat that report the way you would treat the evidence behind any signed contract: it is what you would rely on if the document were ever disputed, so keep the report — or at least the untouched .adoc original — rather than a printout.

One popular trick deserves a caveat. Because ADOC is a ZIP package, you can rename document.adoc to document.zip and browse the contents with any archive tool — the main document, attachments and signature XML files are all there. That is fine for a quick look when you are offline, but it is viewing, not verification: an archive tool tells you nothing about whether the signatures are valid, and unpacking and re-packing the container can easily break its integrity. For anything that matters, verify with a tool that actually validates ADOC signatures — and keep the original file byte-for-byte unchanged.

How to sign a document in ADOC format

To produce an .adoc file, use a tool that creates ADOC containers — the state tool at adoc.archyvai.lt is the reference option. The flow is straightforward: upload the main document, add any attachments and the required metadata, then sign with your eID: a Lithuanian ID card with a reader, a mobile signature (Mobile-ID) or, on platforms that support it, Smart-ID. These means carry qualified certificates, so the signature you create is normally a qualified electronic signature (QES) — the eIDAS level Lithuanian institutions expect on official documents. If eID signing is new to you, our guide to signing with Smart-ID and Mobile-ID walks through how these schemes work.

When several people must sign, the container is passed along and each signer adds a signature to the same .adoc file — every signature lands as its own XAdES file inside the package. Two practical rules keep this clean. First, never edit the underlying document after the first signature: any change invalidates what was already signed, so fix the text before signing starts. Second, make sure everyone signs the same container rather than parallel copies, or you will end up with two half-signed files and no complete document. If an institution asked you for an ADOC, sign in ADOC; if nobody has specified a format, the choice is yours — and worth a moment's thought, as the next section shows.

Where ADOC fits in a contract workflow

The format question is really the last step of a longer chain: a contract is drafted, negotiated, finalised, signed and then kept as evidence. A sensible rule of thumb for the signing step: dealing with a Lithuanian institution → ADOC, usually with a qualified signature; commercial contract with businesses or individuals — in Lithuania or anywhere in the EU — → signed PDF, because every counterparty can open it and most platforms can validate it. More important than the container is that the signature level matches the risk of the document; our guide on choosing between SES, AES and QES covers that decision in detail.

This split is exactly what DokDesk is built around. DokDesk is a secure contract workflow for the Baltics and the EU: reusable templates become contracts, both sides negotiate one live version instead of emailing drafts back and forth, and the final document is e-signed under eIDAS — at SES or AES level with EU national eIDs such as Smart-ID and Mobile-ID — through a secure link that requires no account from the other side. Every step is recorded in a court-ready evidence base, and data stays in the EU under GDPR. DokDesk does not issue qualified signatures; when a procedure demands a QES in ADOC form, the state tools described above are the right instrument. See how signing works in DokDesk for the details.

In practice the two worlds coexist. The same company that runs its commercial agreements through a contract workflow will still receive .adoc files from institutions and will occasionally need to produce one. Handle both with the same discipline: verify signatures with a proper tool, keep originals unchanged, and preserve the surrounding trail — who signed, when, and in what capacity — because the file format alone does not tell that story. What makes an agreement defensible is a signed file plus a verifiable record of how it came to be signed; the container it ships in is secondary.

Frequently asked questions

What is the difference between an ADOC file and a signed PDF?: A signed PDF embeds the signature inside the document itself, so the file stays an ordinary PDF that opens anywhere. An ADOC file is a container: a ZIP package holding the original document, structured metadata and detached XAdES signature files. That makes ADOC flexible — it can carry any supported content type, attachments and multiple signatures — but it needs software that understands the format. In Lithuania's public sector ADOC is the standard; for commercial and cross-border contracts a signed PDF is usually the more practical choice, because every counterparty can open it without special tools.
Is a document signed in ADOC format legally valid?: The container does not decide legal validity — the signature inside it does. Under eIDAS, an electronic signature cannot be denied legal effect merely because it is electronic, and a qualified electronic signature has the same legal effect as a handwritten one across the EU. ADOC documents signed with Lithuanian eID means normally carry qualified signatures, which is why institutions accept them. Whether a specific document meets the form requirements of a specific transaction depends on the law that applies to it — see our overview of when e-signatures are legally binding in the EU. This is general information, not legal advice.
Can I open an .adoc file without special software?: Partly. ADOC is a ZIP package, so renaming document.adoc to document.zip lets any archive tool show the contents — the main document, attachments and signature XML files. That is enough to read the document, but it verifies nothing: you cannot tell whether the signatures are valid or the content untampered. For actual verification, upload the file to the free state tool at adoc.archyvai.lt or to another service that validates ADOC signatures, and keep the original file unchanged — repackaging the ZIP by hand can break the container's integrity.
What should I do if my counterparty cannot open an ADOC file?: This happens often outside Lithuania, where ADOC tooling is largely unknown. If the document is not yet signed and no institution requires ADOC, the simplest fix is to sign a PDF instead — it opens everywhere and supports embedded signatures. If the ADOC already exists, send your counterparty the file together with a link to the free verification tool at adoc.archyvai.lt. What you should not do is print, scan or convert the signed document: the result loses the electronic signatures entirely and has to be treated as a mere copy.
How do I check who signed an ADOC document and when?: Upload the file to the state verification tool at adoc.archyvai.lt or to Lithuania's e-government portal epaslaugos.lt. The verification report lists each signer, the data from their certificate, the time of signing, any timestamps, and whether each signature is valid and at what level. If the report flags a problem — an expired certificate at signing time, altered content, a broken signature — do not rely on the document and ask the sender for a properly signed version. For contracts, keep the verification result together with the original file as part of your evidence.