Thank you for feature request, we'll consider it. Though it's pretty complex task, as, for example, PDF is not really a text file, but a graphical file with vector coordinates of text. Searching in PDF file is always slow. Did you noticed how slow Adobe Reader is slow on searching text even within tiny document? That's because it has to "recognize" text by coordinates which exhausts CPU resources. Now imagine that need to search within hundreds of files, that would be never ending process. Oh course, we can cache text recognition results, but, will it will lead to great slowdowns on attaching files, and, especially on upgrades from older app versions.