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Differences between PDF and PDF/A formats

PDF and PDF/A are closely related formats, but they are designed for different purposes. A standard PDF can include a wide range of interactive, multimedia, security, and external features. PDF/A is a standardized subset of PDF designed specifically for long-term preservation of electronic documents.

PDF/A is defined by the ISO 19005 family of standards. Its goal is to preserve a document's static visual appearance over time, independently of the software and systems originally used to create, store, or display it.

PDF/A does not allow encryption

Unlike a standard PDF, a PDF/A-conforming document cannot be encrypted.

Encryption is useful when a document needs to be protected from unauthorized access. For long-term preservation, however, encryption creates a potential dependency: the document may become inaccessible if the necessary password, key, encryption technology, or supporting software is no longer available.

For this reason, PDF/A does not permit encryption of the PDF file itself.

If an archived document contains sensitive information, access controls should generally be managed by the document-management or archival system rather than by encrypting the PDF/A file.

PDF/A minimizes external dependencies

One of the most important differences between PDF and PDF/A is that PDF/A is designed to preserve the resources required to reproduce the document's visual appearance.

Resources necessary for rendering the document—such as fonts, images, and relevant color information—generally need to be contained within the PDF/A file rather than depending on external resources.

This makes a PDF/A document more suitable for long-term preservation because its appearance is less dependent on software, fonts, color profiles, or other resources that may disappear or change in the future.

However, this does not mean that PDF/A files cannot contain hyperlinks. Links to websites and other external locations can exist in PDF/A documents. The important distinction is that external resources must not be required to reproduce the document's preserved page appearance.

PDF/A restricts interactive and executable content

Standard PDF supports features such as JavaScript, multimedia, encryption, file attachments, forms, and other interactive content.

PDF/A places restrictions on these features because dynamic behavior can make long-term reproduction less predictable.

The exact restrictions depend on the version of PDF/A being used.

For example, PDF/A-1, PDF/A-2, and PDF/A-3 do not permit JavaScript actions. PDF/A-4 can preserve JavaScript actions, but conforming viewers must not execute them automatically.

Embedded files also vary between versions. PDF/A-1 prohibits embedded files, while later standards introduced support for attachments. PDF/A-3, for example, can contain arbitrary file types as attachments. PDF/A-4 also provides mechanisms for preserving embedded files, including the PDF/A-4f conformance level.

Because the capabilities differ between versions, it is more accurate to think of PDF/A as a family of archival standards rather than one format with a single set of restrictions.

PDF/A improves long-term reproducibility

These requirements are intended to make PDF/A documents more reliably reproducible in the future.

A conforming PDF/A file contains the information required to preserve its intended static visual appearance without depending on the original application or computing environment.

However, PDF/A does not guarantee that a document can never be modified. A PDF/A file can be edited, and a modified file can remain PDF/A-compliant if the changes continue to satisfy the applicable PDF/A standard.

Likewise, PDF/A does not guarantee preservation for a specific period such as 25, 50, or 100 years. Instead, the standard reduces technological dependencies that could prevent documents from being reproduced accurately over time.

Long-term preservation still depends on appropriate storage, file-integrity checks, migration practices, backups, and archival policies.

PDF/A versions

PDF/A has evolved alongside the PDF specification.

The main versions are:

  • PDF/A-1 (ISO 19005-1:2005): Based on PDF 1.4 and the original PDF/A standard.
  • PDF/A-2 (ISO 19005-2:2011): Based on PDF 1.7 and supports additional PDF capabilities.
  • PDF/A-3 (ISO 19005-3:2012): Extends PDF/A-2 by allowing arbitrary file types to be embedded.
  • PDF/A-4 (ISO 19005-4:2020): Based on PDF 2.0 and designed to preserve documents using newer PDF capabilities.

PDF/A-4 also defines specialized conformance levels. PDF/A-4f supports embedded files, while PDF/A-4e is intended for engineering documents and can support interactive 3D content.

The appropriate PDF/A version therefore depends on what needs to be preserved and the requirements of the organization or archival system receiving the document.

PDF/A vs. PDF/X

PDF/A should not be confused with PDF/X. Both are standardized subsets of PDF, but they solve different problems.

PDF/A is designed for long-term preservation, while PDF/X is designed for reliable exchange of files used in professional printing and graphic arts.

PDF/X places requirements and restrictions on areas such as fonts, color spaces, output conditions, and other print-production information so that a receiving printer can reliably reproduce the intended result.

Modern PDF/X standards include PDF/X-4 and PDF/X-6, with PDF/X-6 based on PDF 2.0.

Some documents can conform to both PDF/A and PDF/X when they satisfy the requirements of both standards.

PDF or PDF/A: which should you use?

A standard PDF is usually appropriate when the document is intended for everyday viewing, sharing, editing, signing, or interactive use.

PDF/A is more appropriate when long-term preservation is a primary requirement, such as for:

  • Government and public records
  • Legal and regulatory documents
  • Business records
  • Research and academic archives
  • Invoices and financial records subject to retention requirements
  • Digital libraries and institutional archives

PDF/A does impose additional restrictions compared with ordinary PDF, but those restrictions serve a specific purpose: reducing dependencies on technologies that may not be available in the future.

For everyday document workflows, standard PDF remains highly flexible. You can sign PDF, fill in PDF forms, convert JPEG to PDF, or convert PDF to CSV, PDF to text, PDF to JSON, and other formats.

For documents that need to remain reliably reproducible over the long term, PDF/A provides a standardized archival alternative.