Hello,
thank you for the file. Your text file is saved in the Chinese ANSI encoding (GBK) without an encoding mark, and it contains only one Chinese word. The program that read the text file for the conversion therefore guessed a Western encoding, and the two characters became "±¸·Ý". Notepad++ detects the encoding correctly, so it shows the text correctly. PDF24 does not convert text files itself yet, it lets Microsoft Word open them or prints them with the program that is set for .txt files in Windows.
Please save the text file as UTF-8 with BOM (in Notepad++ in the menu "Encoding") and convert it again. Then the encoding is marked in the file and the characters should come out correctly.
A built-in conversion for text files that detects the encoding by itself is on our to-do list. Thank you for the report.