To correct at least one extraneous or missing space in a document, weights are assigned to tokens contained in a dictionary. Each token is defined by an ordered sequence of non-space symbols. The weights are assigned based on at least one of a token length and frequency of occurrence of the token in the document. Corrected text is generated from text of the document by applying an ordered sequence of symbol-level transformations selected from a group of symbol-level transformations including at least (i) deleting a space, (ii) inserting a space, and (iii) copying a symbol. The ordered sequence of symbol-level transformations is optimized respective to an objective function dependent upon the weights of tokens of the corrected text.