ie. You can own the surface rights, but you sell the timber rights to farmer John for 25 years. The nature of the status of the land is fixed by law, and are distinguished as being either a freehold estate or a non-freehold estate. Freehold means ownership without limitations to duration.
The acronym PDF stands for 'Portable Document Format'. This long form of the acronym still doesn't tell you a lot, but it can give you a rough idea of what we are talking about. One thing that you can grasp easily is that it's a 'Document Format'.
Free PDF Creator is essentially a printer driver that lets you save or print documents in the PDF format from the Print properties dialog of any file. However, it also has a setup interface, a compact box that lets you select a destination for finished files and access the PDF-based Help file.