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PDF Glossary

Descriptions for commonly occurring terms when dealing with PDF and related software.

V. Subhash

• alternate description: An alternate description is text in a human-readable form, typically used by applications such as those running a text-to-speech engine or providing accessibility to persons with disabilities.
• annotation rectangle: An annotation rectangle is a rectangular area on a page where an annotation is located or displayed.
• annotation handler: An annotation handler is a software module used to govern the behavior of an annotation type. A PDF viewer application has annotation handlers for all standard annotation types. For additional annotation types, handlers can be provided as plug-in extensions.
• appearance stream: An appearance stream is a rectangular area of page elements used to specify the appearance of an annotation or a form field. It is typically used to provide an alternate appearance to an annotation or form field.
• bounding box: A bounding box is the smallest rectangle that can fit all contents of a PDF page element.
• crop box: A crop box defines a region on a page for display on a screen or printing on paper. Any content between the crop box and the page boundaries is meant to be clipped or omitted. (Also see media box.)
• dash pattern: A dash pattern is a series of dashes and gaps representing a path. It is specified in terms of the lengths of the dashes and gaps, and distance (phase) into the pattern where the dashes begins.
• destination: A destination is a particular "view" on a given document. The view is determined by:
  • page that needs to be displayed
  • location of the viewer application window on the page
  • zoom applied when displaying the page
• form XObject: A form XObject is a PDF content stream representing a self-contained description of a sequence of graphic objects, typically used to economically limit the size of the PDF file and to aid caching of such reusable objects in PDF applications. (See appearance stream.)
• go-to action: A go-to action is a PDF action that makes the viewer application to change the current view to a specified destination.
• glyph: Description of how a character, an accent mark or a ligature is represented in a typeface.
• Javascript action: A Javascript action is a PDF action that makes the viewer application compile and execute a JavaScript script.
• launch action: A launch action is a PDF action that makes the viewer application executes an application or opens/prints a file with its default application. Launch actions are currently supported by Adobe only on Microsoft® Windows^™ platform.
• markup annotation: A markup annotation is a class of annotation types which specify text to "mark up" PDF documents. Certain annotation types such as sound annotations are markup annotations while others such as watermark annotations are not. The text used to mark up PDF documents is useful when extracting the document's contents for applications such as those providing accessibility to persons with disabilities.
• media box: A media box is the part of a PDF page that represents the physical dimensions of the medium on which a PDF page is printed. (Also see crop box.)
• miter: A triangle that is formed by the ends of two lines when they meet at an angle.
• named action: A named action is a PDF action that are specified simply by its name in the document and are expected to be executed by viewer applications that display the PDF actions. In PDF 1.6, a few named actions have been designated for:
  • navigating to next page
  • navigating to previous page
  • navigating to first page
  • navigating to last page
  All PDF viewer applications are expected to support these named actions. Individual viewer applications may support named actions other than those specfied in PDF 1.6 but they are considered as non-standard named actions i.e., unless and until Adobe includes them in a future PDF version.
• path: A path is a line or a boundary of a shape, trajectory, or region. A path is made up of subpaths consisting of straight or curved line segments.
• PDF action: A PDF action is an action specified in a PDF document and is meant to be executed by a viewer application for a specified action event or trigger.
• remote go-to action: A remote go-to action is a PDF action that makes the viewer application display a specified destination in another document.
• URI action: A URI action is a PDF action that makes the viewer application make the shell application of the operating system (explorer.exe in Microsoft Windows) to resolve a uniform resource identifier (URI).
• viewer application: A viewer application is a software application, such as Adobe® Reader, that can render a PDF document on the screen and allow the user to interact with it.