PDF Glossary
A quick reference guide to common PDF terms and acronyms. Each term includes a link to the relevant tutorial where you can learn more.
- Annotation
- A comment, highlight, stamp, or drawing added to a PDF without changing the original content. See our free annotation guide.
- Bates Numbering
- Sequential numbering applied to legal documents for identification in discovery proceedings.
- Bookmark
- A clickable table-of-contents entry that jumps to a specific page or section within a PDF.
- CMYK
- Cyan, Magenta, Yellow, Key (black) — the color model used for professional printing.
- DPI
- Dots Per Inch. Measures image resolution; 300 DPI is standard for print, 72—150 DPI for screen viewing. See how DPI affects file size.
- Embedded Font
- A font file stored inside the PDF so it displays correctly even on systems that do not have that font installed.
- Flatten
- Merging all annotations, form fields, and layers into a single, uneditable layer. Useful before sharing final documents.
- Metadata
- Hidden information stored in a PDF: author, title, creation date, and keywords. Viewable under File → Properties.
- OCR
- Optical Character Recognition. Converts scanned images of text into searchable, selectable text.
- PDF/A
- An ISO-standardised version of PDF designed for long-term archiving. Embeds all fonts and prohibits external dependencies. Read our PDF formats guide for all variants.
- Raster
- An image composed of pixels (e.g., a scan or photo). Contrasts with vector graphics.
- Redaction
- Permanently removing sensitive information from a PDF so it cannot be recovered.
- Vector
- Graphics defined by mathematical paths rather than pixels. Scales infinitely without quality loss.
- Watermark
- A semi-transparent text or image overlay, often used to mark drafts or confidential documents. See how to add watermarks.