If you compile the piece of code given below using pdflatex, then open the resulting PDF file with your preferred viewer, copy the word "efficient" and paste it in a text editor, you will read "efcient". This does not happen with xelatex or lualatex. Is there a way to fix this issue with pdflatex?
\documentclass[fleqn,10pt]{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{libertine}
%\usepackage{lmodern}
\begin{document}
efficient
\end{document}
\input glyphtounicode \pdfgentounicode=1
.