When Adobe Systems Inc. released the PDF format in 1993, the printing and publishing industries changed drastically. Yet, even before the PDF, there existed its predecessor, an already revolutionizing print technology out on the market: the PostScript page description language. Unlike previous printing methods and systems, Adobe PostScript was designed to be independent of device, platform and resolution.

Before PostScript, printing and publishing industries went through tedious, multi-step processes, that were hindered by proprietary page description languages, unique typesetter font libraries, and expensive typesetting systems requiring complex programming. However, with Adobe PostScript came an alternative to those conditions that eventually surpassed the printing methods and systems of the 1980’s.

How The Page Description Language Works

This success is largely due to the way in which the technology works. With a PostScript enabled printing device (a postcript printer), the onscreen appearance of the document is retained when printed onto a page. When the digital information of a document is sent to the printing device, the PostScript printer driver on the computer first encodes it into a PostScript file (.ps) which keeps the formatting of the document regardless of the authoring application being used. This file then gets sent through a Raster Image Processor (RIP) within the PostScript enabled printer, which will then transform the data within the .ps file into a form the printer can produce. Essentially, this is done by generating a high resolution raster image of the document compiled of a series of individual dots, or a bitmap raster image. The printer can then output the file as an image version of the on screen document using a postcript viewer. With Encapsulated PostScript files (.eps), you can include a Post Script image to be included as part of the page that is sent through the RIP. Postcript fonts can be viewed using the Postscript viewer.

However, Adobe later modified this PostScript language to work on a different level. With the growth of Internet publishing, Adobe created and launched an even more groundbreaking technology: the Portable Document Format. This PDF Format is composed of a cut down of the PostScript language, a font embedding subsystem and a structured storage subsystem as well.

In the file format version, PostScript works in very much the same way as it does for printing devices. Yet, where desktop publishers are interested in the transmission and viewing of digital files, the actual PostScript printing device becomes unnecessary. As such, there is no printer RIP to translate the encoded PostScript file into a physical form of output. Instead, the generation of a PDF file (being converted from a regular document file) is done through a PostScript Interpreter that uses the CPU to do the rasterizing in place of the printer RIP. The generated raster image, in this case, is in the form of the PDF, which is essentially the image of a document. Thus, when a document is converted into a PDF, it is digitally “printed” as a file using the virtual printer driver of the PDF conversion software being used. With PostScript as one of the key technologies underlying the PDF structure, the format is able to transfer the look, content and formatting of digital documents across systems and platforms.

Undoubtedly, the innovation of PostScript increased the proliferation and productivity of the print publishing industry and led to the creation of de facto standards. The page description language was solidified as a top industry solution, and eventually became standardized by the International Standards Organization (ISO).