Write a LaTeX macro to differentiate the text

Question

I'm writing a report, and, for editorial purposes, I would like to use different fonts for each part of the report. I think I need to write a macro for it, but I don't know how to have this effect:

\begin{editLater}
//Use times font for this

\end{editLater}

Or

\begin{finalVersion}
//Use new roman font for this

\end{finalVersion}

Answer 1

You can use the font switch macros \rmfamily, \sffamily etc. to switch the font inside the current group. You can define your own environment using \newenvironment.

Changing to a different totally different font locally is more complicated. You should load all font packages with the main font last and then need to rename certain font macros like \rmdefault below.

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{mathptmx} % Times
\usepackage{lmodern}  % LaTeX modern

\usepackage{blindtext}% dummy text

\newenvironment{editLater}{%
    \def\rmdefault{ptm}\rmfamily
}{}
\newenvironment{finalVersion}{%
    \rmfamily
    %\sffamily
}{}

\begin{document}

\blindtext

\begin{editLater}
\blindtext
\end{editLater}

\begin{finalVersion}
\blindtext
\end{finalVersion}

\end{document}

Answer 2

Same as Martin's answer but uses versions to switch over after editing to final version. I could not resist myself from posting, so kindly bear with me.

\documentclass{article}
\usepackage{lipsum} %% Provides dummy text
\usepackage[T1]{fontenc}
%-------------------------------------------------------
\newenvironment{editLater}{\fontfamily{ptm}\selectfont}{\par}
\newenvironment{finalVersion}{\fontfamily{cmr}\selectfont}{\par}
%-------------------------------------------------------
\usepackage{versions}
% \excludeversion{editLater} %% uncomment this line if you want final  version alone
%-------------------------------------------------------

\begin{document}
%% once you edit completely, change editLater to finalVersion inside braces.
\begin{editLater}
\lipsum[1-2]
\end{editLater}
\begin{finalVersion}
\lipsum[3-4]
\end{finalVersion}
\end{document} 

Edit

This uses comment package.

\documentclass{article}
\usepackage{lipsum} %% Provides dummy text
\usepackage[T1]{fontenc}
%-------------------------------------------------------
% \newcommand{\editLater}[2]{{\fontfamily{ptm}\selectfont #2}}
% \newcommand{\finalVersion}[2]{{\fontfamily{cmr}\selectfont #2}}
%-------------------------------------------------------
\newenvironment{editLater}{\fontfamily{ptm}\selectfont}{\par}
\newenvironment{finalVersion}{\fontfamily{cmr}\selectfont}{\par}
%-------------------------------------------------------
\usepackage{comment}
%\excludecomment{editLater} %% uncomment this line if you want final  version alone
%-------------------------------------------------------

\begin{document}
%% once you edit completely, change editLater to finalVersion inside braces.
\begin{editLater}
\lipsum[1-2]
\end{editLater}
\begin{finalVersion}
\lipsum[3-4]
\end{finalVersion}
\end{document}