PDF/A archiving: what it asks, and who supplies what

In plain words

Written for anybody, with nothing taken for granted. It says what the standard is for and what it changes on the document you end up with.

A PDF is not obliged to carry everything it needs. It may name a typeface it does not carry, describe a colour as whatever this particular screen calls red, or point at a picture stored somewhere else. Today all of that works. In fifteen years the typeface is on no machine, the screen is a museum piece and the address answers nothing, and the document is a different document.

So a separate set of rules was written to close every one of those doors. It is called PDF/A, and the promise is short: everything the document needs is inside the document. Public archives, courts and accounting departments ask for it by name.

The good news for whoever has to produce one is that most of it happens without being asked. You state that the document is archival, and the lettering goes in, the colours are described, the document's own description is written, and anything the standard forbids stops the file from being written at all rather than passing quietly. What stays with you is a short list, and every page of this section says exactly where the line falls.

The four claims

Two questions settle which one you want. Does the document have to be read out loud by software? Does it have to carry another file inside it? If neither, the plainest claim is the right one.

The four claims, and what each one adds
Claim	Published text	Version it settles	What it adds	Asked for over the network as
`PDF/A-3B`	ISO 19005-3	PDF 1.7	The page looks the same for as long as the file exists, and the document may carry another file of any kind inside it. This is the claim an electronic invoice is written under.	`pdfa3b`
`PDF/A-3A`	ISO 19005-3	PDF 1.7	The same, and the document also carries the structure of its own text, so it can be read aloud and searched by paragraph rather than by word.	written by the engine; planned for a future version of the request format
`PDF/A-4`	ISO 19005-4	PDF 2.0	The edition built on the current version of the format. It drops the levels, says what it is in one place instead of two, and takes a carried file only where that file is itself archival.	`pdfa4`
`PDF/A-4F`	ISO 19005-4	PDF 2.0	The same edition, for a document that carries files of any kind. It asks for at least one.	written by the engine; planned for a future version of the request format

For a developer

The same thing without the detour: what the claim settles, where the refusals happen, and what the wire format exposes today.

The claim is a document-level statement. It settles the PDF version, it makes the description packet be written, it makes an output intent be written whether or not one was stated, and it turns a set of rules from advisory into blocking.

There are two moments and they run the same rules. A report can be asked for on the document as composed — nothing is written, nothing is changed, and the document need not have claimed anything — and it comes back with every finding at once, each naming the published text, what stands in the way and which font, layer, page, link, field or cell it is about. Then, at write time, a document that did claim is refused on the first finding rather than written wrong.

Through the rendering service the claim is archive, and it takes pdfa3b or pdfa4. The two remaining claims are written by the engine and are planned for a future version of the request format: level A needs a structure tree a request does not yet describe, and the level for carrying files needs a carried file other than the invoice a request already carries.

Nothing here calls a document conforming. An empty report is not a certificate: what the engine does not know to look for, it does not report. The verdict belongs to a validator that did not write the file, and every archival document published on this site is put through one.

Family by family

Eight pages, one family of requirements each, at the same three depths as this one. Each ends on the published texts it answers to.

The requirements group naturally. Take them in this order and each one rests on the last: choose the claim, then the lettering, then the colours, then the page itself, then what its marks stand for, then what it carries, then what it says about itself, and last how the whole thing is checked.

The eight families

Which part of the archiving standard to claim The archiving standard is a family, not a single rule. Four of its members can be claimed here, and choosing between them takes two questions.
Every letter the document draws travels inside it A document that carries its own lettering opens the same way on a machine that has never had that typeface installed. That is the first thing the standard asks for, and the one that changes the file most.
Colours that mean the same thing on every device Numbers on a page are not colours until something says what device they were chosen for. An archival document carries that statement inside it.
A page that comes out the same for everyone The promise of an archival document is that two readers, twenty years apart, see the same page. That holds only where nothing on the page is left for the reader to settle.
The document says what its marks stand for A page of ink says where the marks went and nothing about what they mean. The level that is read aloud, and the accessibility standard, ask the document to say it.
A document that carries other files inside it Part 3 exists because a document sometimes has to carry another file inside it, and that file has to come back out years later, whole.
What the file says about itself A document kept for thirty years is found again by what it says about itself, not by the folder it happened to be in.
Checking the claim, before and after Claiming a standard is one line inside the file. What makes the claim worth anything is that something independent agrees with it.

Where to go next

Why archiving rules exist, and who is obliged to follow them Which colour profiles are accepted as an output intent The electronic invoice, which is an archival document carrying its own data How a request asks for an archival document

See a document that carries its own structure See an archival form

See the prices See the examples

Glossary

standard: A rule argued out in committee, published under a number anybody may buy and read, and identical for every firm claiming it. A claim to follow one can therefore be checked against the text. A way of working that merely spread because it worked is a habit of the trade: useful, widespread, and answerable to no text at all.
PDF/A: A PDF made to be readable in twenty years' time. Everything it needs is inside the file — the fonts, the colours, the description of what it is — so nothing it depends on can go missing later. Public bodies and archives ask for it by name.
veraPDF: A free program that checks whether a file really is what it claims to be, against the published rules. It is the tool archives use, so it is the one used here: a document is not called compliant because we say so, but because veraPDF passed it.
Factur-X: An invoice that is a page for a person and a data file for a machine, in one document. The page looks like any invoice; inside, the same amounts are attached in a form accounting software reads without anybody retyping them. French law requires this exchange between companies.
attachment: A whole file tucked inside a PDF and carried along with it, the way a paper clip holds a sheet to a folder. Opening the document is enough to get it back out. An electronic invoice works this way: the page a person reads carries the same amounts as a file accounting software reads.
output intent: The colour profile written into a document to say which press or which screen its colours were chosen for. A printer reads it to know what the numbers in the file are meant to look like, and the rules on documents kept for the long term ask for one.
font: The drawing of every letter, digit and mark a document writes, held in a file of its own. A PDF carries the fonts it is set in inside itself, which is why it opens looking the same on a machine that has never had them. Leave them out and a reader puts another font in their place, and the layout moves.
structure tree: The list, held inside a tagged PDF, that says what each part of the page is and what it belongs to: this block is a section, this line its heading, this run of cells one row of that table. It is the shape of the document, kept apart from the ink.
request: One call to the service: you send what the document should say, and get the document back. Your bill counts these calls, one for each document. The number of pages inside a document is never counted.
layer: A named group of things drawn on a page that a reader can switch on and off, like tracing paper laid over a plan. A drawing can hold its measurements on one and its notes on another, and a layer can be set to show on screen and stay off the printer.

Every word the site explains

The archiving standard, and who supplies what