For a long time pdflatex  has offered the command \pdfannot  for inserting
arbitrary PDF annotations. However, the command is presented in
a form where additional knowledge of the definition of the PDF format is
indispensable. This package is an answer to the – occasional – questions
in newsgroups, about how one could use the comment function of Adobe
Reader. At least for the writer of LATEX code, the package offers a convenient
and user-friendly means of using \pdfannot  to provide comments in
PDF files. Since version v1.1, pdfcomment.sty  also supports:
LATEX → dvips → ps2pdf, LATEX → dvipdfmx, XeLATEXand LuaLATEX.
Unfortunately, support of PDF annotations by PDF viewers may vary.
The reference viewer for the development of this package is Adobe Reader.