How can you set the -R in your LESS environment variable?

Taken from the manpage:

Options are also taken from the environment variable "LESS".  
For example, to avoid  typing  "less  -options  ..."
each time less is invoked, 

you might tell csh:

   setenv LESS "-options"

or if you use sh:

   LESS="-options"; export LESS

If you are using Bash which is the default on a variety of distributions we can therefore do:

export LESS="-R"

If you want to make this permanent across shell/login sessions then you need to add the command(s) above to the appropriate file, with Bash as the example again you'd open up $HOME/.bashrc with a text editor and drop in the export command. This means each time Bash invokes it will run the export command, setting your Less preferences.

Hope that helps :-)