... include gd pictures in TeX

   Please consult the section on printing

... place legends

   You may use the command GDESCR to place them interactively
   or statically with the line tag GDESCR: in the input file.
   Both methods offer legends with frames with their FRAME command parameter.

... plot functions with gd

   Arithmetic operations with the data columns in the input file
   allow 1-dimensional functions to be plotted.

... make thicker lines

   Use the display parameter CMODE() to make thick characters.
   Use the display parameter LINEWIDTH() to increase the base linewidth.
   Use the T linemode in the data block headers of the input file to specify lines of multiple thickness.

... make larger symbols

   Use the display parameter SYMBOL() to increase the symbol size.

... make larger axis descriptions

   Use the display parameter AXFAC() to enlarge the axis description.
   Often AXFAC(1.5) already gives acceptable results, in particular for overhead slices.

... produce picture overlays

   There is a whole chapter on overlays describing this issue.