There are many ways to improve quality, however the cleaner the source, the better and less intensive the extraction process will be.
Our products contain a set of filters (such as despeckling, skewing, etc) that can help clean up a document, but again, it is always best to start at the source by adjusting your scanning device settings to accommodate.
If you are working with documents of a suitable quality then the second thing to ensure is that resolution is adequate. Read our Knowledge Base Article on selecting the right resolution to ensure optimum quality.
Link to this article http://umango.com/KB?article=54