Howtoforge published a tutorial about how to create fillable forms in ONLYOFFICE Docs 7.0.
How to create fillable forms in ONLYOFFICE Docs 7.0
ONLYOFFICE Docs is an open-source office suite distributed under GNU AGPL v3.0. It comprises web-based viewers and collaborative editors for text documents, spreadsheets, and presentations highly compatible with OOXML formats.