What is a PDF file?
A PDF is a fixed-layout document: fonts, images, vector drawings and page geometry are stored so that the page looks the same in any viewer, on any screen or printer. That predictability is why contracts, invoices, forms, manuals and academic papers are exchanged as PDF rather than as editable files.
Inside, a PDF is a tree of objects: pages, content streams with drawing operators, embedded fonts, images and metadata. Text can be real text with a font, or just a picture of text in a scanned page; the difference decides whether you can search, copy or convert the content.
When PDF is the right choice
Strengths
- Looks identical everywhere: layout, fonts and colours are locked in the file
- Supports forms, digital signatures, bookmarks, links and annotations
- PDF/A variant is accepted for long-term archiving by libraries and authorities
Limitations
- Hard to edit: text reflow and layout changes need a converter or a dedicated editor
- Scanned PDFs carry no text layer until OCR adds one
- Files with embedded fonts and high-resolution images grow large quickly
How to open a PDF file
Every modern browser opens PDF files directly, as do Preview on macOS and the built-in reader on Windows, iOS and Android. For form filling, annotation or signing, use a dedicated reader; to change the text itself, open the file in Edit PDF or convert it first.
How to convert a PDF
To edit the content, convert to an editable format: PDF to Word for text documents, PDF to Excel for tables. For scanned pages, OCR PDF to Word recognizes the text first. PDF to PNG turns pages into images, and PDF to PDF/A prepares a file for archiving.