1. A computer implemented method of extracting structural label and value pairwise data associated with a digital version of a document, the method comprising: a) performing a layout analysis of the digital version of the document to generate one or more layout structures associated with the document, each layout structure including a plurality of structural elements vertically or horizontally aligned where each structural element is defined as a typographical box including one or more lines of textual elements associated with the digital version of the document; b) processing the one or more lines of textual elements to identify and tag textual elements associated with label and value pairwise data; c) processing the one or more layout structures and associated tagged textual elements to generate one or more respective label:value sequences of tagged textual elements representative of a respective layout structure; and d) extracting label and value pairwise data from the one or more label:value sequences of tagged elements, wherein step c) generates the one or more respective label:value sequences of tagged textual element using a sequence-based method to hierarchically segment a sequence of elements associated with the generated one or more layout structures associated with the digital version of the document; and wherein the sequence-based method includes: generating a set of n-prams from the sequence of elements, an n-gram including an ordered sequence of n features provided by a sequence of n named elements; electing sequential n-grams from the set of n-grams, the sequential n-grams defined as similar contiguous n-grams; selecting a most frequent sequential n-pram from the elected sequential n-grams; and generating a new sequence of the elements by matching the selected most frequent sequential n-gram against the sequence of elements associated with the document, replacing matched elements of the sequence of elements with a respective node, and associating the matched elements of the sequence of elements as children of the respective node.