There is only one file type that uses the .ODTTF extension:
Obfuscated OpenType Font
Font file format used in the XML Paper Specification .XPS file and Microsoft Office 2007 formats; stores an obfuscated OpenType font that is based on the fonts used in the original document.
The ODTFF format is an embedded font format, which means that it is included inside an electronic document, such as a .PDF or .DOCX file. It is mainly used as a resource in XPS files. However, the format uses the subsetted font, which means only the characters that are used in the document layout are included in the font file.
Updated: August 10, 2020