PDF Glossary

Clear, jargon-free explanations of the concepts behind PDF files — what they mean, why they matter, and which tool to reach for. A reference for everyone from students to document professionals.

How PDF Compression Works

PDF compression shrinks a file's size without changing what the document looks like to you. To understand why some PDFs collapse to a fraction of their…

PDF Encryption and Passwords Explained

PDF encryption protects a document by scrambling its contents so they can only be read with the right key. Unlike a sticky note that says "please don't…

PDF Metadata and Flattening Explained

Two PDF concepts cause a surprising amount of confusion: metadata (the hidden information describing the document) and flattening (permanently baking…

PDF Page Sizes: A4, Letter, Legal and More

Every page in a PDF has a defined size, and unlike a web page that flows to fit your screen, that size is fixed and absolute. It is baked into the file in…

PDF vs Word: When to Use Each

PDF and Word (DOCX) solve two different problems. A Word document is a recipe: it describes the content and lets the reader's software lay it out. A PDF…

Raster vs Vector in PDFs

A PDF is a container, not a single kind of image. Inside one file you can have crisp text, mathematically described line art, and pixel-based photos, all…

What Is a Fillable (AcroForm) PDF?

A fillable PDF is a document that contains interactive form fields — clickable boxes you can type into, checkboxes you can tick, and dropdowns you can…

What Is a PDF?

A PDF (Portable Document Format) is a file format for documents that look the same everywhere. Open one on a phone, a laptop, a printer, or a ten-year-old…

What Is OCR (Optical Character Recognition)?

OCR, or Optical Character Recognition, is the process of converting an image of text into actual, machine-readable characters. When you scan a page or…

What Is PDF/A and When Do You Need It?

PDF/A is a version of PDF designed for long-term archiving. It is defined by the ISO 19005 standard, and its single goal is simple: a file you save today…