This sounds like a font issue. The PDF is probably using the OpenType fi ligature in the word define, and the current font of the destination application is missing that glyph.
I don't know if there's an easy way to get Acrobat to decompose the ligature on copy.
Your problems with printing are probably also font-related. Something's probably allowing the printer to substitute the document's font with its own built-in fonts and the printer's version of the font is also missing that particular glyph. You'd have to tell Windows to always download fonts to the printer to work around this problem.
Another possibility when printing: UniScribe may not be enabled. MS KB 2642020 talks about this and some possible workarounds (namely, to use RAW type printing rather than EMF type printing). Though the context is slightly different than your specific problem, the cause may be the same and the same workarounds may apply.