This service uses LibreOffice and Unoconv for file conversion.
Supported file types should include the below however for a full updated list of supported formats, please refer to the LibreOffice documentation
Microsoft Word: (DOC, DOCX, DOT, DOTX)
Microsoft Excel: (CSV, XLS, XLSX, XLT, XLTX, SLK, DIF)
Microsoft PowerPoint: (PPT, PPTX)
OpenDocument Formats: (ODT, OTT, ODS, OTS, ODP, OTP, ODG, OTG)
Plain Text: (TXT, TEXT, XML)
Rich Text Format: (RTF)
Images: (BMP, GIF, JPEG, PNG, TIF, PBM, PGM, PPM, RAS, XBM, XPM, SVG, SVM, WMF)
HTML: (HTML)
Lotus Word Pro: (LWP)
StarOffice: (SDA, SDC, SDD, SDW, STC, STD, STI, STW, SXD, SXG, SXI, SXW)
Other: (DBF, FODS, VSD, VOR, VOR3, VOR4, UOP, PCT, PS, PDF)
https://help.libreoffice.org/latest/en-US/text/shared/guide/supported_formats.html