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By PDFWix Editorial Team · April 2026
Plain-English guide to the Portable Document Format — how PDF works, why it became the global document standard, and when you should and shouldn't use it.
PDF — Portable Document Format — was invented by Adobe co-founder John Warnock in 1991 to solve a single problem: how do you send a document to someone and trust that it will look exactly the same on their machine as it did on yours?
The first version shipped in 1993. By 2008 the format was open and standardised as ISO 32000-1, and today there are an estimated 2.5 trillion PDFs in existence — more than every Word document, spreadsheet and slide deck combined. For a quick reference on PDF-specific jargon, see our PDF glossary.
A PDF is a self-contained package: text, fonts, vector graphics, raster images and form data, all glued together with a tiny rendering language derived from PostScript.
Because fonts are embedded, a PDF opened on a Windows laptop, an iPhone and a 1995 Solaris workstation will render with the same line breaks, the same kerning and the same colour profile.
Use PDF when fidelity matters more than editability: contracts, invoices, academic papers, government forms, archival records, anything you'd print.
Avoid PDF when collaboration matters more than fidelity. Use Google Docs or Word for living documents and only export to PDF at the end.
DOCX is editable but renders differently depending on Word version, installed fonts and operating system — open a DOCX written in Word 2014 inside Word 2024 and headings often shift by a line. PDF freezes the layout and embeds the fonts, so the file you sent is the file your recipient sees, byte for byte, with no surprises.
JPG and PNG preserve appearance but lose every benefit of structured text: no copy-paste, no Ctrl+F search, no screen-reader access, no clickable links, and a 5–10x file size for the same page. PDF combines fixed layout with selectable text in a small file — that is why it became the default for contracts, invoices and government forms worldwide.
Skip PDF for living documents that multiple people edit — meeting notes, draft proposals, shared spreadsheets. The format is read-optimised, not edit-optimised; round-tripping through PDF, Word and back to PDF degrades formatting every cycle and breaks revision tracking.
Also avoid PDF for mobile-first content like marketing pages and product docs. PDF pages don't reflow on small screens, so readers must pinch and pan, which kills engagement. Use HTML for anything you'd read on a phone. If you need light edits to an existing PDF instead of converting it back to Word, our Edit PDF tool handles most fixes in the browser.
Not all PDFs are equal. The PDF specification has evolved through versions 1.0 to 2.0, each adding capabilities. Most files you encounter today are PDF 1.4 to PDF 1.7. PDF 2.0 (ISO 32000-2) is the current standard, published in 2017.
You may also encounter specialist PDF subtypes. PDF/A is an ISO standard for long-term archiving — it embeds all fonts and prohibits encryption, ensuring the file is self-contained and readable in 50 years. Government agencies and courts often require PDF/A for submissions. PDF/UA is the accessibility standard, ensuring screen readers can navigate the document structure correctly. PDF/X is the print production standard used by commercial printers and publishers.
PDF files grow large when they contain high-resolution scanned images, embedded fonts, or complex graphics. A 20-page scanned contract might be 15MB while a 20-page text-only contract might be 80KB — the difference is entirely due to image data.
To reduce PDF size: PDFWix Compress PDF runs in your browser and reduces most PDFs by 60–90% without visible quality loss. Choose Recommended compression for everyday use, or High compression to reach portal upload limits. See our complete guide to compressing PDFs for file-size-specific advice.
PDFs support two types of password protection. An open password (document open password) prevents anyone from opening the file without the correct password. A permissions password restricts what an authorised reader can do — preventing printing, copying text, or editing. Both are supported by the AES-256 encryption standard.
Password protection does not make a PDF permanently secure — permissions passwords in particular can be removed by several tools. For genuine data removal, use PDFWix Redact PDF to permanently delete sensitive text from the file structure, not just cover it with a black box. Read more on our security and privacy page.
Yes, with the right tool. PDFWix's Edit PDF tool lets you change text, add images, redact, sign and reorder pages directly in the browser.
Because fonts and layout are embedded in the file itself, not loaded from the operating system.
Yes. Open the PDF in Edit PDF to change text, add images, redact content and re-save. The original file is untouched — you download a new copy with your edits flattened in.