Google has worked out a way to perform OCR (Optical Character Recognition) on any scanned documents that are stored in Adobe's PDF format.

The OCR technology allows for the picture of text (as you get with a scan) to be converted into words that can be searched and indexed.

In the past, scanned documents were rarely included in search results as Google says it could not be sure of their content.

Google says that every day, people all over the world post scanned documents online - everything from official government reports to obscure academic papers.

The company says: "this is a small but important step forward in our mission of making all the world's information accessible and useful".