13. A non-transitory computer program product having instructions encoded thereon that when executed by one or more processors cause a process to be carried out, the process comprising: receiving, by the one or more processors, input data representing a fixed layout digital publication in a first page layout format, the fixed layout digital publication including a plurality of words, each word being formed by a series of glyphs, each glyph having an effective width associated with the first page layout format and a default width associated with a second page layout format that is different than the first page layout format; computing, by the one or more processors, a letter spacing adjustment value for each word individually based on the number of glyphs in the respective word, the effective width of each glyph in the respective word in the first page layout format, and the default width of each glyph in the second page layout format; and generating, by the one or more processors, output data representing the fixed layout digital publication in the second page layout format by assigning the letter spacing adjustment value to a Cascading Style Sheet (CSS) ‘letter-spacing’ property associated with all of the glyphs in each respective word, such that the spacing between each glyph is the default width associated with the second page layout format adjusted by the letter spacing adjustment value on a word-by-word basis.
16. The non-transitory computer program product of claim 13 , further comprising generating a <span> tag associated with each word, wherein the output data includes the <span> tag.