Questions with this tag are about the uses and problems with using the
soul package for letterspacing, underlining, overstriking and highlighting, perhaps with the use of colour. Answers may show the use of
soul but could also deal with limitations and alternative means to achieve the desired end.
soul is included in current versions of both TeX Live and MikTeX.
From the preamble to the
soul documentation (e.g. on CTAN):
This article describes the soul package, which provides hyphenatable letterspacing (spacing out), underlining and some derivatives such as overstriking and highlighting. Although the package is optimized for LaTeX2ε , it also works with Plain TeX and with other flavors of TeX like, for instance, ConTeXt. By the way, the package name
soulis only a combination of the two macro names
\so(space out) and
\ul(underline)---nothing poetic at all.