pdfpreview
I recently needed to search for a string enclosed in square brackets in a PDF document. So I typed [concept] into the search field (including the square brackets).
The result surprised me, as I got a list of pages containing the word concept with all letters contained in that word highlighted in yellow.
I haven't been able to find any documentation of this "feature" – or any other special syntax in the search field.
What is the straight explanation for this behaviour, if any?
iBooks for iPad currently doesn't support highlighting in PDFs. However, there are many 3rd party apps like iAnnotate PDF, GoodReader, or PDFpen that support PDF highlighting and annotating. I use GoodReader and I can personally verify that PDF highlights that were made on Mac's Preview do show up on the GoodReader iPad app.
I also tested the DropBox iPad app and PDF highlights do not show up.
Hopefully, Apple will add PDF highlighting to a future version of iBooks. If enough people request this feature at the Apple feedback site, maybe they will add it in the near future.
Just like you would with a Google search, use the double quotes operator to tell Preview the result must be an exact match.
In your case, for example, typing "formation water" should yield the desired result.
Best Answer
Sounds like the search is actually a Regular Expression search, and by enclosing your search term in brackets, instead of searching for the word 'concept' you were searching for the presence of the letters 'c', 'o', 'n', 'e', 'p' and 't'.