There is only one file type that uses the .OTX extension:
theWord Encrypted Old Testament Text Module
File used by theWord, a free Bible reading program; stores a copy of the Old Testament in an encrypted format; differs from an .OT file, which uses a plain text format; can be used for protecting copyrighted content when distributing digital copies of the Old Testament.
OTX files are commonly downloaded as ".otx.exe" files, which self-install the Old Testament copy when run.
Updated: April 27, 2012