Pega 7.1.7 is supported upto Office 2013 (32-bit).
As for 7.1.8 + the following note is copied from the above referenced platform support guide:
Microsoft Office Support in Pega 7.1.8 and later
Pega 7 has migrated to file-based integration with Microsoft Office and productivity software suites. Beginning in version 7.1.8, Pega 7 supports any version of MS Office that can read and interpret .docx, .xlsx, and .csv files. Any version of MS Office which supports these file formats can be used. There are a few optional developer tools available in Designer Studio that may require additional thirdparty components. For details on which tools are affected and the required third-party components, please see the PDN article Client-side technologies in Pega 7.1.8.