PDF/A: when archive PDFs make sense in Switzerland

An electrician in Wil is moving to paperless bookkeeping. Invoices, receipts and contracts are to be filed as PDFs from now on, for ten years. His fiduciary mentions an acronym: PDF/A. Is it necessary? And is it enough?

Both questions have a short answer. PDF/A is a format made for long-term retention, and it can fit that purpose well. But the law does not prescribe it, and a format alone does not meet everything the retention rules ask for.

What PDF/A is

The PDF Association, the industry body behind the format, describes the purpose of the ISO 19005 standard like this: it defines a PDF-based file format, PDF/A, that represents electronic documents in a way that preserves their static visual appearance over time — independent of the tools and systems used to create, store or render the files.

It does this by specifying which PDF features may be used and how. An archive PDF should look the same in twenty years, even when the program it was made with no longer exists.

The variants

PDF/A is not a single standard but a series. The PDF Association describes the parts like this:

Part	Based on	Particularity
PDF/A-1	PDF 1.4	The original version from 2005; no transparency
PDF/A-2	PDF 1.7	Newer PDF features; attachments must themselves be PDF/A or plain text
PDF/A-3	PDF 1.7	Like PDF/A-2, but allows arbitrary attachments
PDF/A-4	PDF 2.0	The latest version, with its own level for 3D models

There are also conformance levels. For PDF/A-1, the PDF Association names level b (basic), which ensures reliable reproduction of the visual appearance, and level a (accessible), which additionally improves accessibility and reliable text extraction.

For a small business, this mainly means that PDF/A is not simply PDF/A. When setting up a program, it is worth knowing which part and which level it produces.

What the law requires

The duty to retain records is in the Swiss Code of Obligations. Business books and accounting records, together with the annual report and the audit report, must be kept for ten years; the period starts at the end of the financial year (Art. 958f para. 1 CO). Business books and accounting records may be kept on paper, electronically or in a comparable way, provided they remain consistent with the underlying transactions and can be made legible again at any time (Art. 958f para. 3 CO).

The details are set out in the Ordinance on the Keeping and Retention of Business Records (GeBüV). Some of its principles are particularly important for electronic filing:

• Integrity. Business books and accounting records must be kept so that they cannot be changed without the change being detectable (Art. 3 GeBüV).
• Availability. Until the end of the period, an authorised person must be able to inspect and check them within a reasonable time, and on request they must be made legible without aids (Art. 6 GeBüV).
• Storage media. Permitted are unalterable media such as paper or unalterable data carriers, and alterable media only under conditions — for example if technical procedures such as digital signatures ensure integrity and the time of storage can be proven, for instance by time stamps (Art. 9 GeBüV).
• Checks and migration. Storage media are to be checked regularly for integrity and legibility, and data may be transferred to other formats if completeness, accuracy, availability and legibility are maintained; the transfer is to be logged (Art. 10 GeBüV).

The ordinance does not name a particular file format.

What PDF/A does — and what it does not

PDF/A helps with one of the requirements: that a document can still be read and looks the same in ten years. That fits well with Art. 958f para. 3 CO and with the principles of availability and legibility.

Integrity is a different question. PDF/A describes how a file must be built; it does not describe where and how it is stored. Whether a change would be detectable depends on the storage medium and the procedures listed in Art. 9 GeBüV — such as signatures and time stamps, or an unalterable data carrier. A PDF/A document on an ordinary hard drive that anyone in the office can write to is legible, but not automatically unalterable.

Order in the archive

The GeBüV regulates not only individual files but also the order they are kept in. Archived information is to be separated from current information or marked so that it can be told apart, and responsibility for the archive is to be clearly assigned and documented (Art. 7 GeBüV). The information is to be inventoried systematically and protected against unauthorised access; access and entry are to be recorded (Art. 8 GeBüV).

For a small business, this can look modest: one archive folder per financial year, no longer edited after closing, clear file names, one person responsible, and storage that logs access. The file format is one building block among several.

How a PDF/A is created

Many programs can produce PDF/A. In Word, Microsoft describes an option “ISO 19005-1 compliant (PDF/A)” when saving as PDF; it creates a document in the archiving standard so it looks the same later on another computer. Scanner software often offers PDF/A as an output format.

Whether a file actually meets the standard is shown by a validator. Among the test tools for the standard, the PDF Association lists veraPDF, an open-source PDF/A validator.

When PDF/A makes sense

For the electrician in Wil, a few cases emerge where the format plays to its strengths:

• Scanned receipts that are to stay for ten years while the paper original is thrown away.
• Contracts and invoices that arrive as PDFs and are archived — converting them to PDF/A can make sense if the originals use features PDF/A excludes.
• Documents with embedded files, such as an electronic invoice with machine-readable data attached — PDF/A-3 allows such arbitrary attachments.

Where it helps less: documents kept only briefly anyway, or working files still being edited.

For the business

Which solution a business chooses for its records, and whether it meets the rules, depends on the whole setup: format, storage, access, documentation. The GeBüV also requires the organisation, responsibilities and procedures to be documented in working instructions (Art. 4 GeBüV). For setting up audit-proof filing, a fiduciary is the right person to ask.

The PDF tools we are building will convert, merge and shrink documents — processed in Switzerland, in memory, without any file being kept. For archiving, the interplay of format and storage remains the business’s decision.