The recognition rate is greatly dependent on the document and scanning quality. Taking a closer look at the scanned image is useful to control this quality.
With too light documents, characters get broken up: O may become () etc.
Too dark documents contain very heavy shapes, open letters get closed and too many characters are glued together: c becomes an o etc.
Tip: use the magnifying glass to zoom in on details of the scanned document. (The magnifying glass is also available when you right-click the mouse (Context menu).)
Adjust the quality of the scanned image by modifying the scanning brightness of your scanner.
Scan your documents in greyscale or color when the text is printed on a color background.
Use the command Adjust Image to enhance the scanned image for the OCR process.
With Twain and HP scanners, you can enable the auto-exposure option to automatically adjust the brightness and contrast to the scanned document.