A short history of LaTeX and PDF
LaTeX was written on top of TeX by Leslie Lamport in 1984 and 1985. As Lamport wrote in the preface of his LaTeX manual when comparing LaTeX to its TeX ancestor:
LaTeX adds to TeX a collection of commands that simplify typesetting by letting the user concentrate on the structure of the text rather than on formatting commands. In turning TeX into LaTeX. I have tried to convert a highly-tuned racing car into a comfortable family sedan. The family sedan isn't meant to go as fast as a racing car or be as exciting to drive, but it's comfortable and gets you to the grocery store with no fuss.
This means that the focus of LaTeX is more on content than on pure typography. LaTeX provides ready-made commands for sectioning a document, using cross references, tables, lists etc... These are concepts that are related to authoring, and not publishing.
As we know, LaTeX is a a markup language; this does not describe how it is rendered beyond the original text source file.
The original output format for LaTeX documents was DVI, which means device-independant. As the name suggests, this format does not have tangible output. The intent was originally to let this work to a device driver.
The next step was the divps conversion program, which produced PostScript output from a DVI source. At that time, PostScript was the de facto standard for producing high resolution print. PostScript is an Adobe(r) product.
After promoting PostScript, Adobe developped the PDF file format in 1992. Quoting Wikipedia:
Based on the PostScript language, each PDF file encapsulates a complete description of a fixed-layout flat document, including the text, fonts, vector graphics, raster images and other information needed to display it.
The main intent of the PDF file format is to offer an on screen rendering of a document that is similar to what would be obtained on a printer. Originally, PDF files could be produced from PostScript files through an Adobe program called Acrobat Distiller. While the PDF reader was (and still is) freely available to the public, Distiller was a paying software. In 2008, Adobe issued a public patent license which made it possible to use PDF related patented technologies to implement third party implementation of PDF related software, free of charge.
On the LaTeX side, the pdfTex program, which was released in the late 90s, allows creates a PDF output directly from LaTeX. Today, PDF is the de facto standard for producing output from a LaTeX source.