The compressed tar archives (available from the main GMT homepage) contains all the documentation in PostScript form. For your convenience they are also accessible here as both PostScript files and Adobe Portable Document Files (PDF). The main difference between the files is that the PS files contains the full high-resolution PostScript code for the encapsulated GMT plots, while the PDF files only has the screen-resolution (72dpi) bitmaps but may be viewed online with the free Adobe Reader.