Squeezing/shrinking text horizontally

Question

How can I 'squeeze' or 'shrink' some text horizontally? I've heard of the microtype package but I'm not familiar with its options. I tried playing around with it but I could only get it to shrink the text if it was just about to overflow the line. Is there a way to force-shrink a selected portion of the text?

Example - I have the following document and I want to be able to shrink/squeeze all or some porition of the text:

\documentclass[10pt]{article}
\begin{document}
This is a long line of text. This is a long line of text. This is a
long line of text. This is a long line of text. This is a long line
of text. This is a long line of text. This is a long line of text. 
This is a long line of text.
\end{document}

Answer 1

I'm not sure if this is what you want, but when I needed squeezed text I personally found it more visually appealing to just change the tracking (i.e., the inter-letter spacing, more or less) rather than to actually squeeze the individual letters. My result was a combination of someone's forum reply (don't remember where), the microtype package documentation, and a lot of fiddling around to figure out how it actually worked. I used this to make text more narrow in a table. Here's my code, maybe it'll do for you.

\documentclass[10pt]{article}
\usepackage[tracking=true]{microtype}

%% Narrow letter spacing
\newcommand\narrowstyle{\SetTracking{encoding=*}{-50}\lsstyle}
%% Custom letter spacing
\newcommand\spacedstyle[1]{\SetTracking{encoding=*}{#1}\lsstyle}
%% Normal letter spacing
\newcommand\normalstyle{\SetTracking{encoding=*}{0}\lsstyle}

\begin{document}
This is a long line of text. This is a long line of text. This is a
long line of text. This is a long line of text. This is a long line
of text. This is a long line of text. This is a long line of text.
This is a long line of text.

% \narrowstyle as a shorthand for setting tracking to -50 --
% the result is quite squeezed
\narrowstyle
This is a long line of text. This is a long line of text. This is a
long line of text. This is a long line of text. This is a long line
of text. This is a long line of text. This is a long line of text.
This is a long line of text.

% \spacedstyle{} as a lets you set a custom value, e.g. -25
\spacedstyle{-25}
This is a long line of text. This is a long line of text. This is a
long line of text. This is a long line of text. This is a long line
of text. This is a long line of text. This is a long line of text.
This is a long line of text.

% ...and back to normal
\normalstyle
This is a long line of text. This is a long line of text. This is a
long line of text. This is a long line of text. This is a long line
of text. This is a long line of text. This is a long line of text.
This is a long line of text.
\end{document}