When to use plain PDF, when PDF/A is required for archives, and when PDF/X is needed for commercial print — with conversion tips and validators.
PDF, PDF/A and PDF/X are all the same underlying file format — they differ only in which features are allowed. Plain PDF allows everything: JavaScript, encryption, external font references, transparency, multimedia. PDF/A and PDF/X are subsets that ban features incompatible with their use case (long-term archiving and commercial print, respectively).
Picking the wrong flavour rarely breaks anything immediately, but it can fail compliance audits, get rejected by print shops, or render incorrectly fifty years from now. The good news: converting between flavours is a one-click operation in most tools.
Use plain PDF for the 95% of documents that don't need archiving guarantees or print-shop precision: contracts you'll send today, invoices, internal reports, school assignments, ebooks, anything you'll print on your own printer or read on screen.
Plain PDF supports every feature in the spec, which is exactly why it's a poor choice for archives — a file that depends on JavaScript or web fonts may not render correctly in a future viewer.
PDF/A (ISO 19005) is required by many government agencies, courts, and corporate compliance teams for record-keeping. It bans anything liable to break in 50 years: external font references, JavaScript, encryption, transparency (in older levels), multimedia, and external content.
Three sub-levels exist: PDF/A-1 (the strictest, based on PDF 1.4), PDF/A-2 (adds JPEG2000 and transparency), and PDF/A-3 (allows embedded files like the original Word source). Most archives accept PDF/A-2b. The European Union, US National Archives (NARA), and most national libraries mandate PDF/A for digital deposits.
PDF/X (ISO 15930) is the format your print shop wants. It guarantees that everything needed to print the file correctly — fonts, colour profiles, trapping information — is embedded in the file itself. No missing fonts, no surprise colour shifts.
PDF/X-1a is the most widely accepted (CMYK only, no transparency). PDF/X-4 is the modern standard (allows transparency and ICC colour profiles). If your print shop doesn't specify, PDF/X-1a is the safest bet.
Adobe Acrobat Pro: File → Save As Other → Archivable PDF (PDF/A) or PDF/X. The conversion will warn you about features that need to be removed (e.g. transparency for PDF/X-1a). Free alternatives include Ghostscript (command-line) and LibreOffice (export-as-PDF dialogue with PDF/A toggle).
Validate the result with veraPDF (free, open-source) for PDF/A and pdfX-1a Pitstop or callas pdfaPilot for PDF/X. A file that claims to be PDF/A but fails validation will be rejected by serious archives.
Don't assume your tool produces compliant files just because the dialogue says 'PDF/A'. Always validate. Don't archive in PDF/X (it's for print, not preservation). Don't send PDF/A to a print shop expecting good colour — PDF/A doesn't enforce the colour-management requirements that PDF/X does.
Yes, but the conversion may strip features (JavaScript, encryption) and may need to re-embed missing fonts. Always validate the result with veraPDF.
Slightly — fonts must be fully embedded (not subsetted), which can add a few hundred KB on font-heavy documents.
PDF/A-2b is accepted by virtually every archive and supports modern features. Use PDF/A-1b only if a specific regulator requires it.