I read a lot of technical papers and textbooks in PDF that use standard mathematical notation, and sometimes I'd like to be able to find where a symbol is in the text. The only reason I think this might even be possible is that I can select them with the select tool just the same as any other text. Right now I'm looking at a formula that includes a constant delta, and it would be nice to be able to search the PDF for instances of delta so I can find what the definition is here. I've tried using ascii codes for some things and putting them into the search bar in FoxitReader, but it doesn't find the symbols. I'm willing to use any PDF reader on Windows or Linux that has this functionality.
EDIT: What I mean when I say I've tried to use the ASCII code is that I've used alt+... to type the character (or used the Character Map) and put them into the search bar. No luck.