PDF/A is an ISO-standardized archival format designed to ensure documents remain readable decades from now without depending on specific software or external resources. Converting a regular PDF to PDF/A is a compliance operation โ the converter checks what the file contains, removes or adjusts anything that violates the standard, and produces a self-contained archival version.
What PDF/A Actually Requires
PDF/A imposes constraints that regular PDFs don't. All fonts must be fully embedded โ not just subsetted, but the complete font data. External content is prohibited: no links to external files, no embedded audio or video, no JavaScript, no encryption. Color spaces must be defined with embedded ICC profiles rather than relying on the output device to interpret them. Metadata must follow specific standards. A PDF/A file is completely self-contained and self-describing.
There are several PDF/A variants: PDF/A-1 (the original, most restrictive), PDF/A-2 (allows transparency and JPEG2000 compression), and PDF/A-3 (adds support for embedded files of any format, useful for embedding XML invoice data alongside a human-readable invoice). Which version to target depends on the requirement โ legal and government archiving often specifies PDF/A-1b or PDF/A-2b. When in doubt, PDF/A-2b is a good default that handles most modern documents without the strict limitations of PDF/A-1.
Converting With Adobe Acrobat Pro
Acrobat Pro provides the most thorough PDF/A conversion. Go to File โ Save As โ PDF/A, choose the conformance level (PDF/A-1b, PDF/A-2b, etc.), and save. Acrobat runs a preflight check, flags anything that can't be automatically converted, and reports what changes were made. For issues it can't resolve automatically โ certain embedded multimedia, encryption that conflicts with the standard โ it tells you what's preventing compliance and what you'd need to change.
Acrobat's preflight tool (Tools โ Print Production โ Preflight) gives even more granular control. You can run a PDF/A compliance check first to see the full list of issues before committing to conversion, then decide whether to fix them individually or let Acrobat handle them automatically.
Converting Without Acrobat
Several tools handle PDF/A conversion without an Acrobat subscription. Ghostscript, a free open-source PDF processor, converts to PDF/A via command line: the relevant flags are -dPDFA=2 and -dPDFACompatibilityPolicy=1. This is reliable but requires comfort with command-line tools. For a simpler approach, LibreOffice can export documents directly to PDF/A โ in the export dialog, check the "PDF/A-1a" option under the General tab.
Browser-based converters exist for PDF/A conversion but vary in quality. Some only change the file's metadata header to claim PDF/A compliance without actually fixing the underlying issues โ a file that fails a proper compliance check will still fail after that kind of conversion. For genuine PDF/A compliance that will satisfy an archivist or government requirement, Acrobat or Ghostscript is more reliable than a browser tool.
Verifying PDF/A Compliance
After conversion, verify the file actually meets the standard rather than just assuming the conversion worked. Adobe Reader shows a blue bar at the top of a PDF/A file when it opens, indicating the document is in PDF/A mode. For a more thorough check, the free online tool veraPDF validates PDF/A compliance in detail โ upload the file and it reports which conformance level it meets and lists any remaining issues.
When submitting PDF/A files for compliance with a specific regulation or to a specific institution, always confirm which PDF/A level they require and verify your output meets that exact level. PDF/A-2b and PDF/A-1b are not the same, and a submission that requires PDF/A-1b won't be satisfied by a PDF/A-2b file even though the latter is technically more capable.