FreeOCR : A freeware to extract text from imagesThis tool is a freeware which uses Tesseract OCR Engine to extract text from an image or a pdf file. You can install it in your computer easily using its setup file. This tool supports common image formats and multipage tif format images. You can download it from this link.
SimpleOCR : Another freeware to extract text from imagesThis is is a lightweight tool which supports TWAIN scanning, it means you can scan your documents directly in it and can extract the text from the scanned image. It can detect bold, italic and underlined text easily so that you get your text document with high accuracy as compared with the scanned document. You can download this app from here.
Other Methods To Extract Text From ImagesWell, you may purchase paid software such as Nitro PDF Pro for some more powerful features.You may use Free Online OCR site also to get the text extracted from your image or pdf files.
Here is a video tutorial which I made to show this process: