PDF file format: what it is and how to use it

PDF is the document format of record: fixed layout, embedded fonts and graphics that look identical on every screen and printer on Earth. Learn when to use it and what to choose instead.

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What is a PDF file?

A .pdf file is a document in Portable Document Format, Adobe's 1993 design, now ISO 32000, built to fix one problem: a document that looks identical everywhere. Pages are drawn from a PostScript-derived content stream with fonts and images embedded, so nothing depends on the viewer's system. That is why contracts, forms, papers and manuals all end up as PDF.

When should you use PDF?

  • Final documents: the file nobody can accidentally edit and everybody can print identically.
  • Official exchange: contracts, invoices, government forms, the format of record.
  • Print-ready delivery: fonts, color and layout frozen inside.

When is another format a better fit?

For anything people must edit, DOCX or ODT, since PDF fights editing by design. For reflowable reading on small screens, EPUB adapts; for structured data, not PDF at all. PDF is the endpoint, not the workspace.

The short version: PDF is paper made digital, the final form of a document. Write in something else, publish as PDF.

How to open a PDF file

On Windows

Double-click the file, or open it with Sumatra PDF.

On macOS

Adobe Acrobat Reader opens PDF files on macOS.

In your browser

Open PDF files right in a browser tab or with the dexrr viewer. No install, no upload.

Also opens in

  • Adobe Acrobat Reader
  • Any web browser
  • Foxit Reader
  • Sumatra PDF

View or convert PDF files

A quick preview or a new format. No install, no upload.

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PDF technical details

Full name
Portable Document Format
Extensions
.pdf
MIME type
application/pdf
Magic bytes
25 50 44 46 (%PDF-)
Compression
Lossless or lossy
Developer
Adobe (ISO 32000)
Specification
opensource.adobe.com

PDF questions, answered

How do I open a .pdf file?

Every browser, OS and phone has a PDF viewer built in: Acrobat, Preview, Edge, Chrome. dexrr displays and converts pdf files directly in your browser.

Can I convert PDF files online?

Yes, dexrr converts pdf locally in your browser: PDF to DOCX for editing, PDF to JPG or PDF to PNG for page images and PDF to TXT for text extraction.

Is PDF better than DOCX?

For final delivery, yes: the layout cannot shift and no fonts go missing. For editing, DOCX wins easily. They are the two ends of the document lifecycle.

Can I edit a PDF file?

It is designed to resist editing. Acrobat Pro and dedicated editors can patch text and forms, but for real changes go back to the source document and re-export.

Why is my PDF a scanned image?

Scans are photos of pages, so no text layer exists to copy or search. OCR tools add one afterwards.

Is the PDF format outdated?

No, it is the ISO-standardized, legally entrenched format of record for documents worldwide.