1. A method of partitioning a structured document, comprising: on a server system having one or more processors that execute programs stored in the memory of the server system, under the control of procedures executed by the server system: translating the document into an initial hierarchical data structure in accordance with syntactic elements defined in the document, the initial hierarchical data structure including a plurality of nodes corresponding to the syntactic elements; annotating each node with a set of attributes including geometric parameters, wherein the geometric parameters are assigned in accordance with a pseudo-rendering of the document that identifies locations of semantically distinct regions of the document in accordance with the syntactic elements in the document; and merging the nodes in the initial hierarchical data structure into a tree of nodes in accordance with their respective attributes, including the geometric parameters, and a set of predefined rules, the set of predefined rules including rules for merging nodes having nearby positions in the pseudo-rendering and/or having compatible attributes.