I was just writing an email asking a supervisor about downloading multiple dynamic-link library files. The acronym for these is DLL, and the full spelling, dynamic-link library, is never used. How would this be pluralized, because normally I would just add an s, but DLLs is difficult to understand. Sometimes I add an apostrophe to make it DLL's, but I know this isn't grammatically correct. So my question is, how do I make the acronym DLL (and acronyms in general) plural?