1. A machine-implemented method of processing an electronic document, comprising operating computer hardware to perform operations comprising: receiving logical blocks extracted from the electronic document including a text block comprising text lines each encompassed by a respective bounding rectangle; extending edges of ones of the bounding rectangles to at least one boundary without changing layout relationships among the logical blocks in the electronic document; generating a text layout boundary from extended and unextended edges of the bounding rectangles; and storing a description of the text layout boundary in a machine-readable medium.
1. A machine-implemented method of processing an electronic document, comprising operating computer hardware to perform operations comprising: receiving logical blocks extracted from the electronic document including a text block comprising text lines each encompassed by a respective bounding rectangle; extending edges of ones of the bounding rectangles to at least one boundary without changing layout relationships among the logical blocks in the electronic document; generating a text layout boundary from extended and unextended edges of the bounding rectangles; and storing a description of the text layout boundary in a machine-readable medium. 28. The method of claim 1 , further comprising based at least in part on the text layout boundary generating rules constraining layout variations among implicit logical blocks to approximate the input electronic document in appearance while accommodating variable content.