This was a common thing used when the first word processors came out. They called it 'micro-kerning' and it involved slight adjustment of the letter and word sp

This was a common thing used when the first word processors came out. They called it 'micro-kerning' and it involved slight adjustment of the letter and word spacing. The fit of characters is called 'kerning' and it increases readability - and also the ability to create pages with the copier's ID findable. The document source would create a novel document for each person, and if they leaked it and it was reproduced in a paper, the character spacings could lead to the leaker. This was also used with synonym use as a guise. Most spy types would sanitize their docs with a scanner and paraphrase many of the words.