How to replace blank lines by newline character?

Question

I would like to replace blank lines in a command by the newline character \textCR.

For example:

\documentclass{article}
\usepackage{pdfcomment}

\mypdfcomment[2][]{\pdfcomment[#1]{#2}}

\begin{document}
  \mypdfcomment{first line

  second line}
\end{document}

Here I would like

\mypdfcomment{first line

  second line}

to produce

\pdfcomment{first line\textCR second line}

Background: pdfcomment does not understand blank lines and instead uses \textCR. It would be good not having to care about.

Answer 1

Like this?

\documentclass{article}
\usepackage{pdfcomment}

\newcommand\mypdfcomment[2][]{{%
    \let\par\textCR
    \pdfcomment[#1]{#2}%
  }}

\begin{document}
  \mypdfcomment{first line

  second line}
\end{document}