What is the error? How are you creating the PDF's (Reader doesn't create PDF's)?
I make this pdf file using Autocad. With the "print" "dwg to pdf". But the fault is in the adobe reader can not read the signs. When I drag across text that can read it sees it as text.
This response is always possible by google translate
I would suspect that the fonts used in your file are not being properly embedded, and I don't know if printing to PDF from Autocad has an option to embedd them.