How to make ACM style pdfs searchable?

The developers of the class think that in the last 17 years no progress has been made with fonts.

In lines 1470--1492 they reproduce the package ae.sty, that is obsolete. You can add

\usepackage{lmodern}

to your preamble and solve the problem. The call of cmap is not needed.

\documentclass{acm_proc_article-sp}

\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}

\begin{document}