Which Kannada PDF do you have?
A Kannada PDF exported from a Unicode document has its text inside, and conversion pulls it out. A scanned Kannada PDF has only images, so the pages are recognised first and carry recognition’s error rate. Both upload the same way here. What decides how good the result is, is which of the two you started with.
Documents made in Nudi
Nudi is the Kannada typing software of Kannada Ganaka Parishat, funded by the Karnataka government in 2001 and long the default in its offices and schools. Versions up to 5.0 store Kannada as the font’s own glyph codes rather than as Unicode, so a PDF made with them copies out as Latin symbols. Our legacy converter has a table for Nudi 01 e, which also covers Nudi 01 k. Every spelling in it was drawn in the real font and compared with standard Kannada. Choose Kannada — Nudi 01 e in its script list. A Kannada reader has not yet checked the table, and the converted document says so.
What is preserved
Text, paragraph breaks and reading order are preserved. Fonts and exact page layout are approximated. Ottaksharas and the arkavattu, the reph, are written as standard Unicode Kannada sequences, so any Unicode Kannada font draws them correctly.