There's a whole pile of different gotchas. * identifying characters that won't actually print [white text; zero-size font; beneath another layer; not in printa

There's a whole pile of different gotchas. * identifying characters that won't actually print [white text; zero-size font; beneath another layer; not in printable space]. Once this lead to every letter aappppeeaarriinngg ttwwiiccee.. * text in fonts where a != aa [leaving the text as a complicated substitution cypher; caused by font embedding for only the characters in the document] * text in images * no spaces: have to infer from gaps in letters And these are generated by a whole host of different software with different assumptions, and you never know if there's something else you're missing.