What Is PDF/A? Archival PDF Levels, Uses, and Conversion Tips

PDF/A is a version of PDF built for long-term archiving. The international standard ISO 19005 defines it. A PDF/A file must contain everything it needs to display the same way decades from now. That means embedded fonts, defined colors, no content loaded from outside the file, and no encryption. Ordinary clickable web links are allowed. If an archive, court, or government portal asks for "PDF/A," it wants a file that will still open and look the same long after today's software is gone.

PDF/A doesn't change how a document looks. It limits what the file can contain. An ordinary PDF can rely on fonts installed on your computer, play video, run scripts, or require a password. PDF/A bans the features that could stop the file from displaying correctly in the future.

This guide covers what the standard requires and how its parts (PDF/A-1, -2, -3) and conformance levels (a, b, u) differ. It also explains when you're likely to need PDF/A, how to check whether a file claims to be PDF/A, and the conversion problems people run into most often.

What PDF/A requires, and why

The core idea is that the file must be self-contained, meaning it can't depend on anything outside itself. Each rule guards against a specific way a document can fail years later.

Some rules depend on which part of the standard you use. For example, PDF/A-1 forbids transparency entirely, while later parts allow it.

PDF/A-1, PDF/A-2, and PDF/A-3: the main parts

ISO 19005 has several numbered parts, and each one is a complete standard on its own. A newer part doesn't make files built to an older part invalid.

PDF/A-3 isn't "better" than PDF/A-2, just more permissive. An archive that receives an arbitrary attached file can't promise it will be able to open that file later, so some institutions accept PDF/A-2 but not PDF/A-3. On the other hand, some e-invoice formats are built on PDF/A-3, such as Factur-X and ZUGFeRD. They combine a human-readable invoice and a machine-readable XML file in one PDF.

Conformance levels: a, b, and u

PDF/A-1, -2, and -3 have conformance levels, written as a letter after the part number (for example, PDF/A-2b).

Level b (basic)

Level b guarantees visual reproducibility. The pages will look right, but the standard doesn't promise that the text can be reliably extracted or read aloud. Level b is the most common choice because almost any document can meet it, including a plain scan.

Level u (Unicode)

Level u exists only in PDF/A-2 and PDF/A-3. It adds one requirement to level b: every character must map to Unicode, the universal text-encoding standard. In practice, that means you can search, copy, and extract the text and get the correct characters rather than garbled symbols.

Level a (accessible)

Level a is the strictest. On top of Unicode mapping, the file must be tagged. Tagging means the file contains a logical structure that marks headings, paragraphs, lists, tables, and reading order, and it must state the document's language. Screen readers and reflow features rely on these tags, so level a supports accessibility. A level a file also satisfies level b, and level u in the parts that have it.

You can't get level a just by ticking a box. A converter can only produce good tags if the source document had real structure, such as proper heading styles in a word processor. Converting a scan or a poorly structured PDF to level a usually fails or produces meaningless tags.

When you need a PDF/A file

You need PDF/A when the person or system receiving your file asks for it. For everyday documents there's little point converting unless you're archiving them yourself. Typical situations include:

• Archives and records offices. Many national, state, and institutional archives list PDF/A as a preferred or accepted format for preserving documents.
• Courts and e-filing systems. Some courts and electronic filing portals require or recommend PDF/A. Others only ask for a "text-searchable PDF." The rules vary by country, by court, and sometimes by case type, so check that court's filing rules.
• Government submissions. Some agencies require PDF/A for tenders, permits, or regulatory filings. This also depends on the jurisdiction and the agency.
• Universities. Some institutions ask for theses and dissertations in PDF/A for their repositories.
• E-invoicing. Formats built on PDF/A-3 carry structured invoice data inside the PDF.

If a requirement just says "PDF/A" with no part or level, PDF/A-1b or PDF/A-2b is usually a safe choice. If the portal lists the versions it accepts, follow that list exactly. A system that only accepts PDF/A-1 may reject a PDF/A-2 file, even though the newer file is perfectly valid.

How to check whether a PDF claims PDF/A conformance

Keep two things separate: a file that claims to be PDF/A and a file that actually conforms. The claim is just a few lines of metadata, and any program can write it.

Check the claim

1. Open the file in a full-featured PDF viewer. Adobe Acrobat and several other viewers show a notice when a file claims PDF/A compliance. They often open such files in a read-only mode to discourage accidental changes.
2. Look at the document properties. Many viewers show the declared standard (for example, "PDF/A-2b") in the properties or description panel. Where it appears depends on the app and version.
3. Search the raw file. The claim is stored in XMP metadata as pdfaid:part (the number) and pdfaid:conformance (the letter). Open a copy of the PDF in a plain text editor and search for pdfaid. If you find pdfaid:part="2" and pdfaid:conformance="B", or the same values written as XML elements, the file claims to be PDF/A-2b. If you don't find it, that isn't conclusive, because some files store their metadata in compressed form.

Validate the actual conformance

The only way to know whether a file really meets the standard is to run it through a validator. veraPDF is a free, open-source validator developed with the involvement of the PDF Association, which also publishes background material on PDF/A and validation on its website. Adobe Acrobat Pro also includes preflight checks for PDF/A. A validator lists every rule the file fails, such as "font not embedded" or "missing output intent," and those messages tell you what to fix.

For levels u and a, you can do a quick sanity check without special software. Extract the text with a tool like the free PDF to Text converter. If the extracted text is garbled on pages with real text, the file probably lacks proper Unicode mapping and is unlikely to be a valid level u or a file. An empty result usually means the page is only an image with no text layer. Either way, a validator gives the definitive answer.

How to create a PDF/A file: a worked example

Say a court portal asks for a 30-page brief in PDF/A-2b, and you wrote it in a word processor.

1. Clean up the source. Use real heading styles, remove any linked or embedded video, and make sure the fonts you used are installed.
2. Finish the content first. Add exhibits, bookmarks, and page numbers. Any change made after conversion can break conformance. If the exhibits exist only as separate PDFs, combine everything into one file first, for example with the Merge PDF tool. If that's your situation, skip step 3 and run the merged file through a PDF/A converter (see the paragraph after these steps), then continue with step 4.
3. If the brief is a single document, export directly to PDF/A. Microsoft Word, LibreOffice, and other office suites have a PDF/A option in their PDF export settings. Which parts and levels they offer depends on the app and version. Exporting from the original document gives better results than converting an existing PDF afterward.
4. Skip passwords. Don't set an open or permission password, because PDF/A doesn't allow encryption.
5. Validate the final file. Run it through a validator and confirm that it passes as PDF/A-2b before you upload it.

If you're starting from an existing PDF, including a merged file from step 2, use a dedicated PDF/A converter, such as the "save as PDF/A" or preflight functions in professional PDF software. These tools embed missing fonts when they're available, add a color profile, strip forbidden features, and write the metadata.

Common PDF/A conversion problems

Fonts that can't be embedded

Some fonts carry licensing flags that forbid embedding. Some source PDFs also reference a font that isn't installed on your system. Either way, the converter can't embed the font and validation fails. To fix it, switch to an embeddable font in the source document or install the missing font before converting.

Transparency in PDF/A-1

Drop shadows, semi-transparent images, and many modern design elements use transparency. PDF/A-1 forbids it, so the converter has to flatten those elements, and the result can look slightly different. If the recipient accepts PDF/A-2, use it to avoid the problem.

Encrypted or protected source files

You can't convert a PDF to PDF/A while it's still encrypted. You need the password to remove the protection first. If you don't have it, contact whoever created the file.

Larger file sizes

Embedding fonts (subsets are allowed) and a color profile adds data, so a PDF/A copy is often larger than an original that relied on system fonts. Be careful if you shrink it afterward. General-purpose compressors may rewrite the file in ways that break conformance or drop the PDF/A metadata, so always validate after compressing. The guide to reducing PDF file size explains what each compression method changes.

Editing after conversion

Merging, splitting, adding annotations, or filling in forms with a program that doesn't support PDF/A can quietly break conformance and still leave the PDF/A claim in the metadata. The file then claims to be PDF/A but doesn't comply. If you need to combine documents, do it before the final conversion. The article on merging PDF files covers page order and bookmark issues to sort out at that stage.

Scans without text

A scanned page saved as PDF/A-1b or -2b is valid, but it's only a picture of text. If the recipient needs searchable text, run OCR (optical character recognition) before you convert. Level u or a is technically possible after OCR, but it only helps the recipient if the recognized text is accurate, so proofread the OCR text first.

PDF/A quick reference checklist

• Confirm the exact requirement. Which part (1, 2, 3) and level (a, b, u) does the recipient accept?
• If no version is specified: use PDF/A-2b, or PDF/A-1b for older systems that list only part 1.
• Need searchable text? Choose level u (parts 2 and 3) or level a.
• Need accessibility? Choose level a and start from a properly styled source document.
• Need to attach non-PDF files? Only PDF/A-3 and PDF/A-4f allow it, and some archives refuse those files.
• No passwords, no JavaScript, no embedded video, and no content pulled from external files or URLs.
• Finish all edits, merges, and page additions before converting.
• Validate the final file with veraPDF or a preflight tool. Don't rely on the label alone.
• Validate again after any compression or editing.

Frequently Asked Questions

Can I password-protect a PDF/A file?

No. PDF/A forbids encryption, which includes both open passwords and permission passwords. To control who can see the file, keep it in a secured folder or records system. To show the document hasn't been changed, use a digital signature, which PDF/A allows.

Is PDF/A the same as PDF/X or PDF/UA?

No. They are separate ISO standards with different purposes: PDF/X is for reliable print production, PDF/UA is for universal accessibility, and PDF/A is for long-term archiving. One file can sometimes conform to more than one, for example PDF/A-2a and PDF/UA together.

Can I still edit a PDF/A file?

Technically yes, but any edit can break conformance while the file still claims to be PDF/A. Some viewers open PDF/A files read-only for exactly this reason. If you have to make changes, edit the source document and convert again, or validate the edited PDF before you submit it.

Should I convert all my PDFs to PDF/A just in case?

For everyday documents it's usually unnecessary, and conversion can make files larger or flatten some design elements. It makes sense for records you need to keep for many years or when a recipient requires it. If you archive in bulk, keep the originals and validate the converted copies.

Is PDF/A-4 replacing PDF/A-1, -2, and -3?

PDF/A-4 is the newest part and is based on PDF 2.0, but the earlier parts are still valid standards. Files made to them remain conformant. Many submission systems still specify PDF/A-1 or PDF/A-2, so use whichever version the recipient lists.