Somebody asks you for "a PDF/A", or a print shop wants a "PDF/X-1a", and you realise there is more than one kind of PDF. There is. The ordinary PDF you create every day is flexible by design, which is great for sharing and a headache for long-term storage and professional printing. Specialised versions of the format, called PDF standards, add strict rules so that a file will look the same decades from now or print the same on every press. Here is what they mean in practice.
Standard PDF: flexible by design
A regular PDF follows the ISO 32000 specification, which describes what the format can do. It allows fonts to be linked rather than embedded, content from other files, encryption, scripts, video, forms and much more. Because a PDF can rely on things outside itself, two files that look identical today may behave differently in ten years if a font or a link is gone.
For everyday life, this does not matter. A letter, a menu, a booking confirmation and a brochure work perfectly well as standard PDFs. The specialised standards exist for the cases where "works perfectly well today" is not enough.
PDF/A: built to last
PDF/A (ISO 19005) is the archival version. Its goal is that the document looks the same, and can be opened, many years from now with whatever software exists then. To achieve that, it forbids features that depend on something outside the file:
- All fonts must be embedded in the file.
- No encryption or password protection, so future software can always open it.
- No external content, scripts or audio and video that need other programs.
- Colors must be defined in a device-independent way.
- Metadata must be stored in a defined, standard format.
There are several parts (PDF/A-1, A-2, A-3 and later) and conformance levels such as "b" for visual reproducibility, "u" which adds reliable text extraction and "a" which also requires structure and tagging for accessibility. Governments, courts, libraries and many companies ask for PDF/A when documents must be kept for legal or historical reasons.
PDF/X: for professional printing
PDF/X (ISO 15930) exists to make print jobs predictable. A commercial printer wants to know that every font is inside the file, that colors are specified for the press, and that nothing is left to chance. PDF/X files declare an output condition, such as a particular CMYK profile, and embed fonts and images. Some variants, like PDF/X-1a, also forbid transparency and RGB color so the file is as simple for the press as possible.
If a printer asks for PDF/X, they usually tell you which version and often provide a preset or settings file. Follow it exactly. Printing from an ordinary PDF can work, but colors may shift and fonts can substitute.
PDF/UA and other flavours
PDF/UA (ISO 14289) is about universal accessibility. It requires a tagged structure, a reading order, alternative text for images and clear language information so that screen readers and other assistive technologies can navigate the document. Public bodies and education providers increasingly require it.
You may also meet PDF/E for engineering documents and PDF 2.0 (ISO 32000-2), which is simply a newer edition of the general format rather than a specialised profile.
Which one do you need?
- Sharing a document to be read or printed at home: a standard PDF is fine.
- A tender, court filing, medical record or anything that must be stored for years: ask whether PDF/A is required, and which part and level.
- Sending artwork to a commercial printer: use the PDF/X version the printer specifies.
- Publishing for the public or an organisation with accessibility rules: aim for a tagged PDF and PDF/UA where required.
When unsure, ask the person requesting the file which standard and version they need. The answer is usually in a short checklist.
How to create a PDF/A or PDF/X
The best time to create a conforming PDF is at the moment you export from the original document.
- Microsoft Word: in Save As PDF, open Options and tick the ISO 19005-1 compliant (PDF/A) setting.
- LibreOffice: in the PDF export dialog choose the PDF/A option.
- Design software such as InDesign, Illustrator and Affinity apps include PDF/X presets in their export dialogs.
- Validators check whether a file really conforms. veraPDF is a well-known free, open-source one for PDF/A.
Scans can be converted to PDF/A by scanning software that offers it, usually after OCR.
What our tools do and do not do
It is better to be clear about this. MyPDF tools such as Merge, Compress and Edit Metadata work on regular PDFs. They do not create or certify PDF/A, PDF/X or PDF/UA files, and modifying a conforming file with a general tool can break its conformance. For example, changing metadata, recompressing images or merging with a non-conforming file can leave you with a PDF that no longer passes validation.
If you need a conforming file, edit the source, merge the sources before export, and then export once with the correct settings. Reserve post-processing for ordinary PDFs.
