When I pdflatex text containing "fi", e.g. "infinite", the resulting pdf-file looks correct, e.g. "infinite" is shown in the text. But when I search the pdf file for "infinite", 0 occurrences are found. When I copy "infinite" and paste it, the result is "innite". Searching for "innite" results in 0 occurrences as well.
What causes this behavior? My font not being able to handle ligatures? How can I fix it, such that "fi" is treated the same as any other letter combination?