You'd be surprised seeme. With Microsoft's new EULA, most PC venders are shipping Office as a paid upgrade. Now, when you buy a PC, you get Word 2002 only.
As for PDF's, seeme is right. They were made for two reasons, portability and security.
PDF's can be read on any PC with the free reader.
Since PDF's are images, they can be encrypted, protected, etc. When creating the documents, the creator has a ton of options to use, such as password protecting it, preventing printing of it, preventing editing of it, digitally signing it (which would make it unreadable to anyone who doesn't have the signature key), and so on.