Windows
There are several ways to upgrade LibreOffice, including the Online Update option available in the LibreOffice application. Any method should be acceptable, but a method has been suggested here as the most reliable way of creating a clean installion at the targeted version for upgrade. This is especially important when using LibreOffice in a carefully controlled environment, e.g. on a production system.
Uninstall the current version of LibreOffice using Windows Add or remove programs
Install the new version of LibreOffice using the standard installation instructions: Install LibreOffice
Remember to check whether configuration of the integration of PhixFlow with LibreOffice needs to be updated: Configuring PDF Conversion