PDF Glossary of Terms
Estimated Reading Time: 5 mins • Last Updated: July 18, 2026
Working with digital documents frequently requires dealing with complex specifications, compression protocols, and image metrics. Below is our comprehensive alphabetical dictionary explaining the core terms used across LovethePDF tool workspaces and guides.
PDF/A (ISO 19005)
An ISO-standardized version of the Portable Document Format (PDF) specialized for the digital preservation of electronic documents. PDF/A differs from standard PDF by prohibiting features ill-suited for long-term archiving, such as font linking (fonts must be embedded) and external references.
Linearization (Fast Web View)
A specific way of organizing a PDF file layout to enable efficient page-by-page loading over the internet. Linearized PDFs allow a web browser to display the first page of the document while the rest of the file continues to download in the background.
OCR (Optical Character Recognition)
A technology used to convert different types of documents, such as scanned paper files, PDF files, or images captured by a digital camera, into editable and searchable text data. It scans the graphic patterns of letters and translates them into machine-encoded characters.
DPI (Dots Per Inch)
A measure of spatial printing, video, or image scanner resolution. Specifically, it refers to the number of individual dots that can be placed in a line within the span of 1 inch. Higher DPI values produce sharper and more detailed images for print layouts.
WebAssembly (Wasm)
A binary instruction format for a stack-based virtual machine. It is designed as a portable compilation target for programming languages like C, C++, and Rust, enabling high-performance client-side processing of heavy operations (like compressing and converting PDFs) directly in web browsers.
PDF Metadata
Administrative and descriptive information embedded within a PDF file that describes the document. Standard metadata fields include Title, Author, Subject, Keywords, Creation Date, Modification Date, and the software used to compile the document.
PDF Layers (Optional Content Groups)
A mechanism in PDF documents that allows content to be selectively hidden or displayed by users or applications. Commonly used in engineering drawings, blueprints, and multi-lingual manuals to toggle specific annotation planes.
Vector Graphics
Computer graphics images that are defined in terms of points on a Cartesian plane, which are connected by lines and curves to form polygons and other shapes. Vector text and shapes can be scaled infinitely in a PDF without pixelation.
Raster Graphics (Bitmap)
An image representation consisting of a grid of individual pixels. Common raster formats embedded within PDFs include JPEG and PNG. Unlike vector graphics, raster graphics lose visual crispness and become pixelated when zoomed in.
OpenXML (DOCX / XLSX / PPTX)
A zipped, XML-based file format specification developed by Microsoft for representing spreadsheets, presentations, and word processing documents. LovethePDF converts PDFs directly into editable OpenXML packages locally in your browser.
PDF/X (ISO 15930)
A specialized subset of the PDF standard designed for high-fidelity graphic technology and commercial offset printing. It ensures that color profiles, layout dimensions, and embedded images match exact pre-press print regulations.
RC4 & AES Encryption
Cryptographic algorithms used to secure PDF documents. Modern PDF specifications support up to 256-bit Advanced Encryption Standard (AES) security to enforce owner restrictions (disallowing copying or printing) and user passwords.