Is there a service / program for searching text in images and pdf files?

Question

Search engines

There are a huge number of pdf, jpg, png files with text. You need to search through these files. Are there ways?

Answer 1

There are programs that index by textual content. However, I'm not aware of any software that can also do OCR, since it's usually a manual process.
Document search engines include DocFetcher, Xapian, and the Apache Tika framework.