Sunday, October 28, 2007
PDF is a file format for representing documents in a manner independent of the application software, hardware, and operating system used to create them and of the output device on which they are to be displayed or printed. A PDF documentconsists of a collection of objects that together describe the appearance of one or more pages, possibly accompanied by additional interactive elements and higher-level application data. A PDF file contains the objects making up a PDF document along with associated structural information, all represented as a single self-contained sequence of bytes.
A document’s pages (and other visual elements) can contain any combination of text, graphics, and images. A page’s appearance is described by a PDF content stream, which contains a sequence of graphics objects to be painted on the page. This appearance is fully specified; all layout and formatting decisions have already been made by the application generating the content stream.
In addition to describing the static appearance of pages, a PDF document can contain interactive elements that are possible only in an electronic representation. PDF supports annotations of many kinds for such things as text notes, hypertext links, markup, file attachments, sounds, and movies. A document can define its own user interface; keyboard and mouse input can trigger actions that are specified by PDF objects. The document can contain interactive form fields to be filled in by the user, and can export the values of these fields to or import them from other applications.
Finally, a PDF document can contain higher-level information that is useful for interchange of content among applications. In addition to specifying appearance, a document’s content can include identification and logical structure information that allows it to be searched, edited, or extracted for reuse elsewhere. PDF is particularly well suited for representing a document as it moves through successive stages of a prepress production workflow.
full pdf overview
PDF Reference, Sixth Edition, version 1.7 (PDF, 31.0M)