Demo version will be a limited version of my software

A shareware would be a great show of all my software can
do, however we know that a shareware can be easily stolen
and used for free.

I think that's why some websites only release the help file
of their softwares.

I appreciate your opinion and also would like the opinion of
someone who has already sold with and without demo and if
the difference of sales is large.

Moises