PDF vs PDF/A: Understanding the Archival PDF Format

The Problem PDF/A Solves

Open a Word document from 2003 in a modern version of Word. Chances are the formatting looks different -- fonts may have shifted, spacing may have changed, features may render differently than they did two decades ago. Now imagine opening a mission-critical document 50 years from now. Will it still be readable? Will the software to open it even exist?

This is the problem PDF/A was created to solve. Standard PDF is already more future-proof than most document formats, but it still allows features that could break long-term preservation: external font references, JavaScript, embedded multimedia, encryption, and dependencies on external content. Any of these elements could become unresolvable when the technology they depend on disappears.

PDF/A (where the "A" stands for "Archive") is a restricted subset of the PDF specification, standardized under ISO 19005, designed specifically for long-term digital preservation. It eliminates every feature that could compromise a document's readability in the future by requiring complete self-containment: all fonts embedded, no external dependencies, no encryption, no JavaScript, and no elements that rely on anything outside the file itself.

For governments, legal firms, healthcare organizations, financial institutions, libraries, and archives, PDF/A is not optional -- it is mandated by regulation or best practice. For everyone else, understanding when PDF/A matters (and when standard PDF is perfectly fine) saves time and avoids unnecessary complexity.

PDF vs PDF/A: Side-by-Side Comparison

The core principle is simple: a PDF/A file must contain everything needed to render it correctly, with no dependencies on anything external to the file. This is what makes it archival -- open the file in 100 years, and as long as software exists that reads the PDF/A specification, the document will look exactly as it did when it was created.

PDF/A Conformance Levels

PDF/A is not a single specification. It has evolved through multiple versions, each adding capabilities while maintaining the archival guarantee.

PDF/A-1 (ISO 19005-1:2005)

The original PDF/A standard, based on PDF 1.4. It is the most restrictive and most widely supported version. PDF/A-1 comes in two conformance levels:

PDF/A-1b (Basic): Ensures visual preservation -- the document will look the same when opened in the future. This is the minimum conformance level and the most commonly used.

PDF/A-1a (Accessible): Includes everything in 1b plus structural requirements for accessibility -- tagged content, logical reading order, and Unicode character mapping. PDF/A-1a documents are accessible to screen readers and assistive technology, making them the preferred choice for organizations with accessibility requirements.

PDF/A-2 (ISO 19005-2:2011)

Based on PDF 1.7, PDF/A-2 relaxes some restrictions from PDF/A-1 while maintaining the archival guarantee:

• Allows transparency (important for documents with overlapping elements)
• Supports JPEG2000 compression (better quality-to-size ratio than JPEG)
• Permits embedding PDF/A files within a PDF/A-2 document (useful for archiving collections)
• Supports digital signatures

PDF/A-2 also comes in three conformance levels: PDF/A-2a (accessible), PDF/A-2b (basic), and PDF/A-2u (Unicode -- requires all text to have Unicode mapping, a middle ground between a and b).

PDF/A-3 (ISO 19005-3:2012)

Identical to PDF/A-2 in most respects, but with one significant addition: PDF/A-3 allows embedding any file type as an attachment. This means you can embed the original Word document, a spreadsheet with source data, an XML data file, or any other file inside the PDF/A-3 container.

This is useful for electronic invoicing (embed the machine-readable XML invoice data alongside the human-readable PDF representation), engineering documents (embed the CAD source files), and scientific publications (embed the datasets).

PDF/A-4 (ISO 19005-4:2020)

The most recent version, based on PDF 2.0. PDF/A-4 simplifies the conformance levels by dropping the separate a/b/u distinctions and introducing two levels:

PDF/A-4: The standard level, equivalent to the former "b" conformance. PDF/A-4f: Allows embedded files (like PDF/A-3).

Which Level Should You Choose?

When in doubt, PDF/A-2b is the safest modern choice. It is well-supported, handles transparency (which PDF/A-1b does not), and satisfies most regulatory requirements.

How to Create PDF/A Documents

From Microsoft Word

Word can save directly to PDF/A:

1. Go to File > Save As (or Export > Create PDF/XPS Document)
2. Choose PDF as the format
3. Click Options
4. Check ISO 19005-1 compliant (PDF/A) (Word typically supports PDF/A-1b)
5. Click OK, then Save

This is the simplest method for creating PDF/A from a Word document. However, Word only supports PDF/A-1b in most versions. For PDF/A-2 or PDF/A-3, you need a different tool.

From LibreOffice

LibreOffice supports PDF/A export:

1. Go to File > Export as PDF
2. In the PDF Options dialog, go to the General tab
3. Check Archive (PDF/A, ISO 19005)
4. Select the desired PDF/A version (LibreOffice supports PDF/A-1b, PDF/A-2b, and PDF/A-3b)
5. Click Export

LibreOffice's PDF/A support is more current than Word's, offering PDF/A-2b and PDF/A-3b options that are not available in most Word versions.

Online Conversion

The PDF converter on ConvertIntoMP4 can produce PDF output from various source formats. For documents that need to be archived, convert from your source format (DOCX, ODT, RTF, HTML) to PDF using the document converter, then validate the output against PDF/A standards using a validation tool.

From Adobe Acrobat Pro

Acrobat Pro provides the most comprehensive PDF/A creation:

1. Open or create a PDF in Acrobat Pro
2. Go to Tools > Standards > Save as PDF/A
3. Select the desired conformance level
4. Acrobat runs a preflight check, identifies any compliance issues, and attempts to fix them automatically
5. Review the results and save

Acrobat's preflight check is the most thorough available, catching issues that simpler tools miss: non-embedded fonts, non-compliant color spaces, transparency issues (for PDF/A-1), and missing metadata.

Converting Existing PDFs to PDF/A

Converting a standard PDF to PDF/A is not always straightforward because the conversion tool must fix any non-compliant elements. Common issues that need resolution:

Missing fonts: The conversion tool must find and embed any fonts referenced but not embedded in the original PDF. If the font is not available, the tool may substitute a similar font, which changes the document's appearance.

Transparency: PDF/A-1 does not allow transparency. Elements with transparency must be flattened during conversion, which can change their visual appearance slightly. PDF/A-2 and later allow transparency, so upgrading to a newer conformance level often sidesteps this issue.

Color spaces: PDF/A requires ICC color profiles. PDFs using device-dependent color spaces (like raw CMYK or RGB without profiles) need color space conversion during the PDF/A creation process.

Interactive elements: Form fields, JavaScript, and multimedia are stripped during PDF/A conversion. This is by design -- the archival format requires static content.

For documents containing form fields that you want to preserve the visual appearance of, flatten the PDF before or during the PDF/A conversion. This embeds the current form field values as static text while maintaining their visual position on the page.

Validating PDF/A Compliance

Creating a file that claims to be PDF/A and creating one that actually complies with the standard are two different things. Validation is essential.

Validation Tools

veraPDF: The industry-standard open-source PDF/A validator. It is the reference implementation endorsed by the PDF Association and provides the most authoritative validation results. Available as a desktop application and command-line tool.

Adobe Acrobat Pro Preflight: Built into Acrobat Pro, the preflight tool validates against all PDF/A conformance levels and provides detailed reports on any compliance failures.

PDF/A Pilot (Callas Software): A commercial tool specifically designed for PDF/A creation, validation, and correction. It can automatically fix many common compliance issues.

Common Validation Failures

Industries That Require PDF/A

Government and Public Records

Many government agencies worldwide mandate PDF/A for official records. The US National Archives requires PDF/A for electronic records submissions. The European Union uses PDF/A extensively in regulatory and legislative document management. Court systems in multiple countries require PDF/A for electronic filing.

Healthcare

Medical records, clinical trial documentation, and pharmaceutical regulatory submissions increasingly require PDF/A. The FDA accepts PDF/A for electronic submissions, and healthcare organizations use it for patient records that must be preserved for decades.

Financial Services

Banks, insurance companies, and investment firms use PDF/A for compliance documentation, contracts, and regulatory filings. Financial regulations often specify retention periods of 7 to 10 years (or longer for some document types), making PDF/A's long-term preservation guarantee essential.

Legal

Law firms and corporate legal departments archive contracts, court filings, correspondence, and case documentation in PDF/A. The format's guarantee that documents will look identical in the future is critical for legal evidentiary purposes.

Libraries and Cultural Institutions

Libraries, museums, and archives use PDF/A for digitized collections, preserving books, manuscripts, photographs, and other cultural materials in a format designed to last. The Library of Congress recommends PDF/A for digital preservation.

When Standard PDF Is Fine

Not every document needs PDF/A. The standard is designed for documents that must be preserved and remain readable for the long term. For many everyday uses, standard PDF is perfectly appropriate:

• Temporary documents: Meeting notes, informal communications, draft versions that will be superseded
• Short-lived reports: Weekly status reports, daily summaries, documents with a useful life measured in weeks or months
• Documents requiring interactivity: Fillable forms, documents with JavaScript validation, multimedia presentations
• Documents requiring encryption: Confidential documents that need password protection -- PDF/A prohibits encryption
• Internal working documents: Documents shared within a team during active projects

The overhead of PDF/A -- larger file sizes due to embedded fonts, restrictions on useful features, validation requirements -- is only justified when long-term preservation is genuinely needed. For documents you will delete next month, standard PDF is the right choice.

Working with PDF/A in Practice

File Size Considerations

PDF/A files are typically 10-50% larger than their standard PDF equivalents because all fonts must be fully embedded rather than referenced. For documents using many fonts or large font families, the size difference can be significant.

If file size is a concern, you can compress the PDF after creation -- but be careful. Some compression techniques can break PDF/A compliance by re-encoding images in non-compliant ways or stripping required metadata. Always re-validate after compression. For general PDF size reduction tips, see our guide on how to reduce PDF file size.

Editing PDF/A Files

PDF/A files can be opened and viewed in any standard PDF viewer. However, editing them requires tools that understand the PDF/A constraints. If you edit a PDF/A file in a tool that does not respect the standard, the edit may break compliance -- for example, by adding a non-embedded font or introducing transparency.

If you need to significantly edit a PDF/A document, the best workflow is: convert to an editable format like DOCX using the document converter, make your changes, then export back to PDF/A. This avoids the complexity of editing within the PDF/A constraints. For details on PDF-to-Word conversion, see our guide on how to convert PDF to Word.

Combining PDF/A Documents

Merging multiple PDF/A files requires a tool that maintains compliance in the merged output. Not all PDF merge tools do this -- some strip the PDF/A identification during the merge process. When you merge PDFs, verify that the resulting file is still PDF/A compliant by running it through a validator.

Frequently Asked Questions

Can I open PDF/A files in any PDF viewer?

Yes. PDF/A is a subset of standard PDF, so any application that can open a PDF can open a PDF/A file. Some viewers display a notification bar indicating the file is PDF/A and may enter a "read-only" mode to prevent modifications that could break compliance. You can dismiss this notification in most viewers.

Does PDF/A support digital signatures?

PDF/A-2 and later support digital signatures. PDF/A-1 supports signatures with some restrictions. Digital signatures in PDF/A use the same technology as in standard PDF -- the signature validates the document's integrity and authenticity. For learning about PDF signatures generally, see our guide on how to sign a PDF online.

Can I convert a PDF/A file back to standard PDF?

Technically, a PDF/A file is already a valid standard PDF -- it just has additional restrictions. You can "convert" to standard PDF simply by removing the PDF/A identification metadata. However, this is rarely necessary since PDF/A files work everywhere that standard PDFs do.

How long will a PDF/A file last?

PDF/A is designed for indefinite preservation. The ISO standard is maintained and updated, and the PDF specification is publicly available, ensuring that future software developers can always build compliant readers. Realistically, PDF/A documents created today should be readable for as long as digital computing exists in a recognizable form.

Is PDF/A the same as PDF/X?

No. PDF/A is for archival (long-term preservation). PDF/X is for print production (reliable color reproduction and print output). PDF/E is for engineering (supporting 3D content and interactive elements). They are different subsets of the PDF specification designed for different purposes.

Wrapping Up

PDF/A exists for a specific, important purpose: ensuring that documents remain readable and visually identical far into the future. For organizations bound by regulatory requirements, for documents with lasting legal significance, and for cultural preservation, PDF/A is the definitive solution.

For everyday document work -- sharing reports, emailing invoices, distributing marketing materials -- standard PDF handles the job perfectly well and offers more flexibility in terms of features, file size, and interactivity.

The practical approach is to create in your preferred format, convert to standard PDF for distribution and short-term use, and convert to PDF/A when a document needs to be preserved for the long term. The PDF converter and document converter handle both conversion paths, and the validation tools ensure your PDF/A files actually comply with the standard they claim to follow.