PDFs, or Portable Document Format files, are a type of document that can be used on all modern computers and operating systems (Mac, UNIX variants, Windows, and others). Their other great advantages are that they will look the same on all computers, and that they can be printed out very well—unlike such things as Word or HTML files. These are the primary reasons why PDFs are used for these net.books, instead of making a regular web page or putting up some other document format.
In order to view and print PDF files, you will need a PDF viewer programme. The most common is Adobe Reader (formerly known as Adobe Acrobat Reader), which is available for most common operating systems, and is often supplied with hardware, or with other software, so there's a good chance you already have it installed on your system. If it isn't, you may want to browse any CD-ROMs that came with your computer, or with programmes you bought later on, to see if one has a copy; alternatively, you can download Adobe Reader for free from Adobe's web site for a large number of different operating systems. You will need version 3.0 or later.
However, there are other PDF viewers available as well if you are not happy with Adobe Reader, some of which are shown below; to find more, go to a search engine (such as Altavista or Google) and search for
pdf AND viewer NOT acrobat—just be sure to get a viewer that can handle PDF version 1.2.
office-type documents, including PDFs, for Palm hand-held computers;
Panther) and can show PDFs as well as many other types of file;
If you do have a PDF viewer on your computer, it will probably have set itself up as a plug-in for your web browser. This means that if you click on a link to a PDF, it will be opened inside your web browser, which may result in difficulties with saving the file to your hard drive.
See the Printing page for information about printing these net.books.