Glossy paper, coloured paper and very granular paper do not scan well. Layout of text - Newspaper style columns work less well than continuous text. Fonts - Size and type. Features such as bold and italic. Simple tables will usually OCR adequately, but graphs, formulae and equations will frequently result in error saturation to the point of complete loss of meaning.
Capture performs poorly with skewed text.
PDF documents maintain the look and layout of the originals, including text, graphics and images. Compresses files - smaller file sizes mean the document downloads quicker, is easier to manipulate and prints quicker. Acrobat Reader can be downloaded and distributed free. It is possible to create full-text indexes of PDF collections that can be searched in Reader. Accessing documents can be slow - depends on the amount of RAM available.