Something like this built in:

http://pdfsearchapp.com

FEATURES

• Page ranking system

• Word distance algorithm

• Keyword placement analyse

• Emphasize power ranking (Header, title, paragraph detection)

• Search specific files

• Higher rank for up-to-date files

• Quick navigation between pages in different documents

• Highlighting keywords in different colours

• Insert annotates to pages (Highlight, Underline, Strikethrough)

PDF Search is an elegant reader app using artificial intelligence algorithms to find the most relevant pages inside thousands of PDF documents quickly. It searches like a human, but it makes it very fast.

Information is a key to success. PDF Search will help you quickly reach the information lying in documents. Just import your documents, reference books, e-mails or notes into it. Then feel the power of accessing any information in seconds inside. You will shine in meetings, classes or at work using your iPhone, iPad or Mac. Everyone will be surprised by your mastery on the documents.

WHAT MAKES IT DIFFERENT

Ordinary search tools makes existency search. They only check whether your keywords exist in documents or not. Then they give you a bunch of document list. You check them one by one whether they are the one you are looking for or not. There is no intelligence, just like a machine.

PDF Search makes relevancy search. Instead of checking only existency, It analyses all pages separately and makes a relevancy check for each of them according to given keywords. This check is similar to how a human checks documents. For example, a human is more interested on a page if it has a title containing keywords. PDF Search combines all these kind of checks into a brand new algorithm. Using this algorithm, it finds the most relevant pages instantly among thousands of documents.