PDF file format
PDF is the format that guarantees a document looks the same everywhere — same page breaks, same fonts, same layout on any screen or printer.
or drag & drop them here · images, video, audio and documents · up to 2 GB
What is PDF?
PDF (Portable Document Format) was created by Adobe in 1993 to solve a problem that plagued early desktop publishing: a document formatted on one machine fell apart on another because the fonts or the printer driver differed. PDF fixes the page. It carries its own fonts, images and vector drawing instructions inside the file, so the layout is settled at export time rather than at open time.
Under the hood a PDF is a descendant of PostScript, the page-description language Adobe built for laser printers. That heritage explains both its strengths and its weaknesses. It is superb at describing where marks go on a fixed-size page, which is why it prints perfectly. It is poor at reflowing content, which is why reading a two-column A4 PDF on a phone is uncomfortable and why editing one is harder than editing the original document.
Since 2008 PDF has been an open ISO standard (ISO 32000), not an Adobe-controlled format, so you do not need Adobe software to create or read one. Every browser renders PDFs natively, and the archival subset PDF/A is the format national archives and courts accept for long-term storage because it forbids external dependencies like linked fonts or embedded video.
| Extension | |
|---|---|
| Category | Image |
| MIME type | application/pdf |
| Released | 1993 |
| Developed by | Adobe |
| Compression | Lossy or lossless |
| Transparency | Yes |
| Animation | No |
PDF: frequently asked questions
- Why does a PDF look identical on every device?
- Because the file carries everything it needs to draw itself: embedded font outlines, image data and exact coordinates for every element. Nothing is resolved from your system at open time, so a missing font on your computer cannot change the line breaks the way it can in a Word document.
- Can I edit a PDF?
- You can annotate, fill forms, sign and reorder pages easily. Editing the actual text is harder, because a PDF stores positioned glyphs rather than paragraphs. For real editing, convert the PDF to DOCX and work there, then export back to PDF when you are finished.
- Why can I not select the text in some PDFs?
- That PDF contains a photograph or a scan of a page, not a text layer. Every letter is just pixels. To make it searchable you need OCR (optical character recognition), which recognises the shapes and adds an invisible text layer behind the image.
- What is PDF/A and do I need it?
- PDF/A is the archival profile of PDF. It requires every font to be embedded and forbids anything that could break over time — external links to fonts, JavaScript, audio, encryption. Use it when a document must still open correctly in twenty years: contracts, theses, official records.
- Do I need Adobe software to open a PDF?
- No. PDF has been an open ISO standard since 2008 and every major browser, phone and operating system reads it natively. Adobe Acrobat adds advanced editing and prepress tools, but for viewing, printing, filling forms and signing, the built-in viewer is enough.
- Why is my PDF file so large?
- Almost always because of images. A scan saved at 600 DPI, or photos embedded at full camera resolution, dominates the file size while the text weighs almost nothing. Re-exporting at 150-200 DPI for screen use, or 300 DPI for print, typically cuts the size by an order of magnitude.