PDF & Adobe Glossary
Clear, concise definitions of key terms in PDF technology, Adobe Acrobat development, and document workflows.
PDF Standards & Formats
PDF (Portable Document Format)
An open file format created by Adobe in 1993 for presenting documents consistently across hardware, software, and operating systems. PDF encapsulates text, fonts, graphics, and metadata into a single self-contained file. It became an ISO standard (ISO 32000) in 2008 and is now maintained by the ISO rather than Adobe. The current version is PDF 2.0 (ISO 32000-2:2020).
PDF/A
An ISO-standardised subset of PDF (ISO 19005) designed for long-term digital preservation of documents. PDF/A files are self-contained — they embed all fonts, colour profiles, and metadata needed for faithful reproduction. JavaScript, audio, video, and external references are prohibited. Common conformance levels include PDF/A-1b (basic), PDF/A-2b (based on PDF 1.7), and PDF/A-3 (allows embedded files of any format). You can convert PDFs to PDF/A online for free using Mapsoft's PDF Hub.
PDF/UA
PDF/Universal Accessibility. An ISO standard (ISO 14289) that defines requirements for universally accessible PDF documents. PDF/UA files must have a complete tag structure, proper reading order, alternative text for images, and correct use of semantic elements. This ensures the document works reliably with assistive technologies such as screen readers, magnifiers, and refreshable Braille displays.
PDF/X
A subset of PDF (ISO 15930) designed for reliable prepress data exchange in the printing industry. PDF/X files must meet strict requirements for colour management, font embedding, trapping, and transparency handling to ensure predictable output on printing presses. Common variants include PDF/X-1a (CMYK-only), PDF/X-3 (allows ICC-based colours), and PDF/X-4 (supports transparency and layers). You can convert PDFs to PDF/X online for free using Mapsoft's PDF Hub.
Tagged PDF
A PDF that contains a logical structure tree describing the reading order and semantic meaning of its content. Tags identify headings, paragraphs, lists, tables, images, and other elements — similar to HTML. Tagged PDF is required for accessibility compliance (PDF/UA) and enables features such as content reflow on small screens, text extraction, and reliable copy/paste.
Linearization (Fast Web View)
An optimisation technique that reorganises a PDF file so the first page can be displayed before the entire file has been downloaded. The cross-reference information and first-page objects are placed at the beginning of the file, enabling byte-serving by web servers. Particularly useful for large documents served over the internet. You can linearise PDFs online for free using Mapsoft's PDF Hub.
PDF Internal Structure
COS Objects
Carousel Object System objects. The low-level building blocks of a PDF file. Every element in a PDF — from page content to font data to metadata — is represented as a COS object. The eight types are: booleans, integers, real numbers, strings, names, arrays, dictionaries, and streams. Understanding COS objects is fundamental to PDF development and manipulation at the API level.
Cross-Reference Table (xref)
A lookup table in a PDF file that provides byte offsets for each indirect object, enabling random access to any object without reading the entire file. Located near the end of the file, it allows PDF readers to jump directly to specific objects. PDF 1.5 introduced cross-reference streams as a more compact alternative to the traditional text-based xref table.
Content Stream
A sequence of instructions in a PDF that describes the visual appearance of a page. Content streams use a postfix (Reverse Polish) notation with operators for placing text, drawing shapes, transforming coordinates, and rendering images. For example, BT /F1 12 Tf 72 700 Td (Hello) Tj ET draws the word "Hello" in 12-point font.
Incremental Update
A method of modifying a PDF by appending changes to the end of the file rather than rewriting it. Each update adds a new cross-reference section and trailer. This preserves the original content and enables features such as undo, digital signature preservation, and audit trails. The trade-off is increased file size over successive edits.
Page Boxes
Rectangular regions defined in a PDF that control how a page is displayed, printed, or trimmed. The five page boxes are: MediaBox (physical page boundary), CropBox (visible area when displayed), BleedBox (area including bleed for printing), TrimBox (intended finished page size), and ArtBox (extent of meaningful content).
Page Labels
A PDF feature that allows pages to display custom numbering schemes independent of the physical page index. For example, front matter can use Roman numerals (i, ii, iii), the body can use Arabic numbers (1, 2, 3), and appendices can use alphabetic prefixes (A-1, A-2). Page labels affect the page number shown in the viewer but not the internal page order.
Document Metadata
Information about a PDF document rather than its visible content. Includes title, author, subject, keywords, creation date, modification date, and the application used to create it. Metadata is stored in the document information dictionary and optionally in an XMP metadata stream, which provides richer, extensible XML-based metadata.
XMP (Extensible Metadata Platform)
An XML-based metadata standard created by Adobe for embedding structured metadata within files. In PDF, XMP metadata streams can contain detailed information about rights management, provenance, workflow status, and custom properties. XMP is the preferred metadata format in modern PDFs and is required by PDF/A for preservation metadata.
PDF Features & Capabilities
Bookmarks (Document Outline)
An interactive navigation feature in PDF documents that provides a clickable table of contents in a panel alongside the document. Each bookmark can point to a specific page, view, or action. Bookmarks can be nested to create a hierarchical structure reflecting the document's organisation. They are formally called the "document outline" in the PDF specification. Mapsoft's Bookmarker plugin automates their creation.
Annotations
Interactive elements overlaid on PDF pages, including text notes, highlights, underlines, strikethroughs, stamps, links, and multimedia. Annotations can be added, edited, or removed without altering the underlying page content. The PDF specification defines over 25 annotation types, each with properties controlling appearance, behaviour, and interactivity.
AcroForms
The original interactive form technology in PDF, introduced in PDF 1.2 (1996). AcroForms support text fields, checkboxes, radio buttons, dropdown menus, list boxes, signature fields, and push buttons. Form fields can include JavaScript for validation, calculation, and formatting. AcroForms remain the recommended form technology in PDF 2.0.
XFA Forms
XML Forms Architecture. An alternative form technology developed by JetForm (later acquired by Adobe) that was included in PDF from version 1.5. XFA uses XML to define dynamic form layouts, data bindings, and business logic. XFA was deprecated in PDF 2.0 and is not supported in most non-Adobe PDF readers.
Digital Signature
A cryptographic mechanism embedded in a PDF that verifies the identity of the signer and ensures the document has not been modified since signing. Digital signatures use public key infrastructure (PKI) and certificate authorities (CAs) to establish trust. PDF supports multiple signature types including approval signatures, certification signatures, and document timestamps.
Named Destinations
Predefined locations within a PDF document that can be referenced by name rather than page number. A named destination associates a string identifier with a specific page view (page, coordinates, and zoom level). Used for creating stable links that survive page reordering, document updates, and cross-document referencing.
Optional Content Groups (Layers)
A mechanism that allows content to be selectively shown or hidden within a PDF document. Each layer can be toggled on or off by the viewer. Used in technical drawings (electrical vs plumbing overlays), multilingual documents, documents with conditional content, and interactive maps. Supported from PDF 1.5 onwards.
PDF Portfolio
A PDF file that contains multiple embedded files of any format — documents, spreadsheets, images, videos — presented in a unified interface with a customisable layout and navigation. Unlike simple file attachments, portfolios provide a structured browsing experience. Commonly used for project deliverables, regulatory submissions, and archival packages.
Transparency
A compositing feature introduced in PDF 1.4 that allows objects to be partially see-through. Transparency encompasses opacity (alpha), blend modes (multiply, screen, overlay, etc.), and soft masks. Content using transparency must be "flattened" for output to devices or formats that do not support it, which can affect visual appearance if not done carefully.
PDF Operations
Flattening
The process of merging interactive elements — form fields, annotations, comments, and stamps — into the static page content of a PDF. Once flattened, these elements become permanent parts of the page image and can no longer be edited or extracted. Flattening is used before archiving, printing, or distributing documents where interactivity is not required. Mapsoft's Flattener plugin automates this process. You can flatten PDF annotations online for free using Mapsoft's PDF Hub.
Redaction
The permanent and irreversible removal of sensitive content from a PDF document. Unlike simple visual masking (drawing a black rectangle over text), true redaction removes the underlying text, images, and metadata from the file so they cannot be recovered by any means. Proper redaction requires specialised tools — standard drawing tools only hide content visually. Mapsoft's MaskIt plugin provides professional redaction capabilities. You can redact PDFs online for free using Mapsoft's PDF Hub.
OCR (Optical Character Recognition)
The process of converting images of text (from scanned documents, photographs, or faxes) into machine-readable, searchable, and selectable text. In PDF, OCR typically creates an invisible text layer placed precisely behind the scanned image, preserving the original visual appearance while making the content searchable and accessible. You can run OCR on PDFs online for free using Mapsoft's PDF Hub.
Bates Numbering
A sequential numbering system applied to documents for identification and retrieval, named after the Bates Automatic Numbering Machine. Each page receives a unique number — typically a prefix followed by a sequential digit (e.g., ABC-000001). Used extensively in legal proceedings, regulatory submissions (particularly FDA filings), and audit documentation. Mapsoft's Impress Pro plugin supports automated Bates numbering.
Preflight
The process of checking a PDF document against a set of rules before output. Preflight detects potential issues with fonts (missing or not embedded), colours (incorrect colour spaces), images (insufficient resolution), transparency (unsupported by output device), and standards compliance (PDF/A, PDF/X). Adobe Acrobat Pro includes built-in preflight profiles, and Mapsoft's FDA Checker performs specialised compliance checking for FDA submissions.
Font Embedding
The practice of including font data within a PDF file so the document displays correctly regardless of whether the viewer has the font installed. Full embedding includes all glyphs in the font; subsetting includes only the glyphs actually used in the document, resulting in smaller files. PDF/A requires all fonts to be embedded.
ICC Profile
An International Color Consortium profile that mathematically defines the colour characteristics of a device or colour space. PDF files can embed ICC profiles to ensure consistent colour reproduction across different displays, printers, and proofing systems. ICC profiles are required in PDF/X for print production and in PDF/A for archival purposes.
Compression & Image Formats
JBIG2
A compression standard (ISO/IEC 14492) optimised for bi-level (black and white) images. JBIG2 achieves compression ratios significantly better than CCITT Group 4 by identifying recurring patterns (such as repeated characters) and storing them once. Widely used in PDF for compressing scanned documents. Supported from PDF 1.4 onwards.
JPEG 2000
A wavelet-based image compression standard (ISO/IEC 15444) supported in PDF from version 1.5. Offers better compression quality than standard JPEG at the same file size, with support for both lossy and lossless compression, region-of-interest coding, and progressive decoding. Commonly used in PDF/A-2 and PDF/A-3 documents.
Adobe Development
Adobe Acrobat
Adobe's commercial software for creating, editing, signing, and managing PDF documents. Available in Standard (basic editing and signing) and Pro (full feature set including preflight, accessibility tools, and forms) editions. Acrobat supports third-party plugins via the Acrobat SDK, enabling specialised functionality such as Mapsoft's product range.
Acrobat SDK
The Adobe Acrobat Software Development Kit. A comprehensive set of APIs, C/C++ headers, sample code, and documentation that allows developers to build plugins extending Acrobat's functionality. The SDK provides access to core PDF operations including page manipulation, content extraction, annotation management, and security. Mapsoft has used the Acrobat SDK to develop its product range for over 30 years.
Acrobat Plugin
A software module that extends the functionality of Adobe Acrobat. Plugins are compiled native code (typically C/C++) that load into Acrobat at startup. They can add menu items, toolbar buttons, custom dialog boxes, and automated processing capabilities. Plugins require a full version of Acrobat (Standard or Pro) — they do not work with the free Adobe Reader.
Adobe PDF Library
A server-side SDK from Adobe (distributed by Datalogics) for creating, manipulating, rendering, and printing PDF documents programmatically. Unlike Acrobat, the PDF Library runs without a GUI, making it suitable for automated workflows, server-side processing, and high-volume document generation. See our Adobe PDF Library development services.
JavaScript in PDF
A subset of JavaScript embedded within PDF documents for interactivity and automation. Used for form field validation, calculations, dynamic formatting, document-level scripting, and event handling. Executed by Acrobat's built-in JavaScript engine, which provides PDF-specific objects and methods not available in browser JavaScript.
UXP (Unified Extensibility Platform)
Adobe's modern extension framework for Creative Cloud applications including Photoshop, InDesign, and XD. UXP replaces the older CEP framework with a more secure, performant architecture. Extensions are built with HTML, CSS, and modern JavaScript, using Spectrum Web Components for consistent Adobe-style UI. See our Spectrum UXP guide.
CEP (Common Extensibility Platform)
Adobe's HTML-based extension framework for Creative Cloud applications. CEP panels are built with HTML, CSS, and JavaScript, with access to host application functionality via ExtendScript or native APIs. While still supported, CEP is being gradually replaced by UXP in newer Adobe applications. See our CEP introduction.
ExtendScript
Adobe's proprietary scripting language based on ECMAScript 3 (JavaScript 1.5). ExtendScript adds features such as file I/O, XML support, and the #include directive. Used to automate tasks across Adobe applications including InDesign, Illustrator, and Photoshop. The ExtendScript Toolkit (ESTK) provided debugging capabilities. Being gradually supplanted by modern JavaScript via UXP. See our ExtendScript guide.
Action Wizard
A feature in Adobe Acrobat Pro that allows users to record and replay sequences of operations for batch processing multiple PDF files. Actions can combine steps such as adding watermarks, setting security, running JavaScript, optimising files, applying redaction, and exporting data. Actions can be shared across teams for consistent document processing workflows.
Work with PDF Professionally
Mapsoft's Adobe Acrobat plugins help you automate bookmarking, stamping, redaction, compliance checking, and more.