Much has been published about good design of information graphics. Tufte's and Stephen Few's books The Visual Display of Quantitative Information and Show Me the Numbers are definitely books you should read if you make graphs and tables of data.
I just finished an equally useful book directed more at the text documents you create. Robin Williams' The Non-Designer's Design Book is definitely a book everyone (including technical people) who creates documents should read. It's easy reading and she gives many simple, concrete examples of how to make your documents stand out. I'm no designer and pride myself on avoiding fancy-shmancy graphics that don't add value but this book points out simple things anyone can do to stand out.
Anything that can help communicate your problem solutions to others effectively is adding value.