PDF (its whole name is Portable Document Format) is file format, which was developed by Adobe Systems company. Their target was to create format, which is capable of operation on any device with any software, because they wanted to create format usable worldwide. Creation of files in this file type is usually as an export from other formats (for example from .odt using OpenOffice.org), but creating of these files can be done in Adobe Reader Pro. It has also its free version, but that one serves only for viewing .pdf files. There are many other possibilities of opening .pdf files. For example you can use some web browsers like Google Chrome. Then there are some programs like PDF-XChange Viewer Pro.
Editation can be done in Foxit PDF Editor. It allows text editing, adds page editing, picture adding, etc. It was first created in 1993 and during next versions, the .pdf format became more famous. There are 11 eleven versions of this file type. Since the first versions, there were many updates and they have bring many news. For example .jpg support, web link support, .pdf password protection. Also there were added many types of fonts, so its almost impossible to find text, which can not .pdf handle.
Nowadays there is a new version being developed and it is called v 2.0.