PDF, PDF/A and the Formats Inside Your PDF

Everyone uses PDFs; almost nobody knows what the letters hide. Ten minutes of vocabulary makes you the person who understands what lawyers, printers and archivists are asking for.

What a PDF actually is

A PDF is a page description: a set of instructions that says "put this text here, this image there, in exactly this typography." That is why it looks identical everywhere — unlike a Word file, it does not re-flow based on the reader's fonts and settings. Inside, a PDF can contain:

• Text as real characters (searchable, selectable, accessible) or as images from scanners (neither — until OCR runs)
• Fonts embedded or referenced (embedded is what makes portability real)
• Interactive elements: forms, links, annotations, signatures
• Structure: bookmarks, tags for accessibility, metadata (author, dates, title)

PDF/A: the archivist's PDF

PDF/A is a strict subset designed to be readable in 50+ years: all fonts embedded, no external dependencies, no encryption, no JavaScript. Courts, governments and libraries demand it for permanent records. Converting to PDF/A is an export choice in most document tools — if a registry asks for it, they are thinking about the year 2076.

Encrypted and password-protected

Two different locks can be applied:

1. User password — the file cannot even be opened without it
2. Owner password — opens freely, but restricts printing/copying

If you own the document, both are manageable with our PDF Unlock; if you need to add protection (with real AES encryption and permission control), PDF Protect does it locally. See our guide on removing passwords honestly for the limits.

"Flattened" and other vocabulary

• Flattened PDF — interactive elements (forms, layers) merged into static content; required by many official submission systems so nobody can edit after signing
• Tagged PDF — contains accessibility structure that screen readers navigate; a legal requirement for public documents in many countries
• Linearized ("Fast Web View") — arranged so browsers can show page 1 before the whole file downloads
• Portfolio — a PDF acting as a folder for other files; supported by Adobe Reader, unreliable elsewhere (extract the files for compatibility)

Which quality matters when

Goal	What to care about
Sending a contract	Text PDF, not scans; encryption only if required
Archiving records	PDF/A, flatten forms first
Email with size limits	Compress (scans shrink 60–85% — guide)
Website download	Linearized + compressed
Printing	300 DPI source, no aggressive compression

Bottom line

A PDF is a chameleon that adapts to the job — contracts, archives, forms, print. Know the four words (PDF/A, encrypted, flattened, tagged) and you already speak the language of the people who process your documents.