PDF is the step-child of PostScript that has come into its own. In fact, it was originally introduced by Adobe as interchange PostScript back in the early 90s as a tool to help create the "paperless" office. Adobe Acrobat, which herded the new file format, was extremely expensive for its day, and therefore did not garner a huge market.
Acrobat was separated into 2 main subprograms: Distiller, which would take a PostScript file and convert it to PDF file; and Reader, which would allow anyone to view the PDF on their screens. Of course, any program could be used to create a PostScript or an EPS file, so the beauty of the Acrobat PDF file combination was that it allowed files to be viewed regardless of the program used to create the original file, as long as the user had Acrobat Reader.
You've got to live in a cave not to know what Acrobat Reader is a free download available from Adobe's website, but it was not always this way. Originally, you had to pay for Reader! Ah, the power of market share. It was absolute marketing genius when adobe made the decision to offer reader for free because this made the mass distribution of readable files easy and accessible, and made Acrobat a household word.
PDF also supports multimedia element like movies / sound. It also supports hypertext elements like bookmarks, links to website address or e-mail. More recently, it supports form and form filling. All of this means that in addition to creating viewable files, it can be used for presentations, samples, manuals and more. Relevant to the engraving industry, PDF files can contain text and images, highly efficient when importing and exporting artwork for the engraving machine. All of these things are fine and dandy but what is most important to us engravers is that it is one of the most reliable means of importing documents from other uers / programs / platforms into your CorelDraw, Adobe Illustrator etc program. The portability of the format allows the easiness to transfer client's logo on the computer and be ready to engrave on an item, ie pewter tankards .