The PDF dictionary uses the Aboriginal Serif font, which lacks the characters subscript one (U+2081, ₁) and subscript 2 (U+2082, ₂). These are needed for some morpheme identifiers. I used FontForge to construct those characters based on the superscript versions, U+00B9 and U+00B2 respectively, in each of the four font variants (regular, bold, italic, bolditalic), and the results seem to be OK.