Include Proximity search for words in the pdf

Here is a sentence in a book (PDF)

"These drugs are used to ameliorate fear during the time of exams"

I want to search this sentence in a big book

As humans we can't remember things as such

I would type "exam fear" in the search bar

This phrase is not as such in the book but I want to glance at it. BUT I WANT TO GET THE RESULTS FAVOURABLE TO THE DESIRED SENTENCE MENTIONED ABOVE

Also,I can't search for the single word 'exam' because it would bring up loads of results.

So here is the idea:

Include an option called 'Proximity search' which could be turned ON/OFF

If it's ON the app must look for a set of words typed in the search bar,even if they are not in the order as present in the book.

It must take each word as keyword and look up for them in proximity (FROM IN A SINGLE LINE TO 2 PAGES)

We could be able to change the level(sesitivity) of the PROXIMITY SEARCH (such as from a line a paragraph etc.)

This would be of great use if u make this on the next update.