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'.
Adobe Reader, or equivalent, is required to view PDF files. Click the Get Adobe Reader image to get a free download of the reader from Adobe.