I cannot search for the word 'define'. It is something special with this word. Maybe a flaw in some regexp? Reproducible: Always Steps to Reproduce: 1. Open a pdf document that contains the word 'define'. 2. Ctrl+f, type in 'define' (without the ' ' of course) and press enter. 3. Try search for any other word in the document. Actual Results: Okular do not find the occurances of 'define' but other words are ok. Expected Results: I expect Okular to find 'define' too.
attach the document you are using
It seems to be known as the 'fi'-problem. The characters f and i, written together, renders quite tight in some fonts, which seems to cause problems. It's not specific to Okular. It happens for instance to adobe acrobat reader to, but only in the browser embedded reader (sic). I guess we can 'define' this problem resolved.
You're probably using an ultra old version of okular, get a newer one
Search for "ligatures fl fi".
They're not just put close to each other, but indeed as fi or fl ligatures, which are separate characters. LaTeX (and probably many other programs) do this on purpose since it looks nicer. It's indeed not specific to Okular but it would be nice to solve it: whenever a search term contains 'fi' or 'fl', just do a second search with those letters replaced by the ligatures?