Graphics Programs Reference
In-Depth Information
PDF is used wherever the exact presentation of the content is important (for example
for a print advertisement or topic). It isn't normally suitable when the content is to be
layed out or reflowed at the last moment, such as in a variable width web page—
languages like HTML and CSS which separate content from presentation are more
suitable in those circumstances.
Other page description languages
Many page description languages were created when the printing of lines of text in fixed
fonts began to be replaced by digital graphics printing. The printer would then process
the language to generate a bitmap at the appropriate resolution. For example, PostScript
(Adobe), PCL (Hewlett Packard), and KPDL (Kyocera). Simpler languages were used
for vector plotters (for example, HPGL from Hewlett Packard).
These languages varied in complexity and functionality. PostScript files, for example,
are full programs—the result of executing the program is the document's visual rep-
resentation. These languages often contain extra instructions to control aspects of the
document other than the page content, for example which tray paper is drawn from or
whether the output is to be duplexed.
Development of PDF
PDF began as an internal project at Adobe to create a platform-neutral method for
document interchange. PostScript was already popular in the print community, but
wasn't practical for on screen use with the computers of the day—especially for random
access (to render page 50 of a PostScript document, one must process pages 1-49 first).
The idea was to use a subset of the PostScript graphics language together with ancillary
data to create a structured language for standalone documents to be viewed on (or
printed from) any computer.
PDF 1.0 was announced in 1993, with Acrobat Distiller (for creating and editing PDF
files) and Acrobat Reader (for viewing only), both as paid-for programs. The US Tax
Authorities started to ship tax forms as PDFs, purchasing a license to allow their users
to download Acrobat Reader for free. Later on, Acrobat Reader was made available to
everybody at no cost, leading to the widespread use of PDF for the exchange of docu-
ments online.
Over the next 10 years, after a slow start as prepress features were added, PDF overtook
PostScript as the language of choice in the printing industry. Today, it is the only general
page description language of note.
Some Advantages of PDF
When a number of formats compete to be the industry standard, the best contender is
not always the victor—luck can intervene. In this case, though, PDF had a number of
singular advantages. We look at some of them here.
