Scan Tailor is free software to improve the results of scanning.
Scan Tailor is an interactive post-processing tool for scanned pages from scanners. It performs operations such as page splitting, de-skewing, adding/removing borders, and others. You give it raw scans, and you get pages ready to be printed or assembled into a PDF, CBZ, or DJVU file. While the program is interactive it can also batch process the images. Output is written in TIFF format and the file size can be quite large depending on the DPI you use. An image processing program may also be needed. A good free one is IrfanView.
Documentation is available in a comprehensive wiki and is available in either English or Russian. The wiki also provides tips for scanning.
 The issues
Scan Tailor fixes typical problems that are encountered when you scan a document. It can also be used if you take pictures with a camera but it will not fix all types of camera problems such as key-stoning where the camera lens is not 90 degrees to the page.
 The steps
The tool provides a sequence of steps to perform on the input images.
- Fix Orientation: ensure all pages a oriented properly, 90 degree rotations can be performed.
- Split Pages: if the scan produced 2 pages in the image this step can split them.
- Deskew: correct tilted pages - can be automatic using lines or borders found on the page.
- Select Content: crop the content to the usable area of the page.
- Page Layout: Select margins and align the data on the page. Batch mode can ensure all pages are the same size.
- Output: Produce the final output files. These are expected to all be the same size and you can set DPI and output format as Black and White, Color/Grayscale, or Mixed.
Output files are in TIFF format. Black and White modes uses G4Fax compression; other modes use LZW compression. G4Fax, and LZW compress without loss of quality.