There are two well-known OCR software available for free namely - SimpleOCR and JOCR but both utilities require user to download and use them from desktop, however there is a better way to get images/documents converted in editable formats using free web-based OCR services, these free services allows users to upload documents in various formats and download editable version in format of their choice.
I tested some of these free online OCR services and here is a list of best ones which will get the job done easily and accurately.