Originally Posted by Billi
I'm not sure if this is historically true. When I remember it right, pdf was invented for sharing documents, to display them on all different PC's and keep the layout, independent from what fonts and so on a user has installed. The usage in print came later, in the first years the most used format there was ps and eps.
PostScript was originally developed as a printer-independent page description language, to allow applications to output highly-complex page images to any printer. The idea was that you'd have software called a "Raster Image Processor" in the printer's firmware, to interpret the PostScript instructions and convert them into pixels for that printer. Used in that way, it was initially popular for 3D graphics applications and desktop publishing. It was only later that it caught on as a format for exchanging documents with other people.