That will depend on the timezone that is used in the microflow with the 'Generate document' activity. If this is done by a scheduled event, it will use the 'Scheduled event time zone' as set in the project settings. If the microflow is triggered by a user, it will use the selected timezone of the user.
Also note that the client (browser) timezone is independent of the timezone that the user selected in his user settings (the association with the System.TimeZone table), if the user has selected the UTC timezone there then it will still render as UTC even if the browser does localize the time correctly.
For further reading, check https://world.mendix.com/display/refguide5/DateTime+handling+FAQ, especially the section "What is the purpose of setting a time zone for a user?". In fact, this exact case is mentioned here: "This means that users should set their time zone to the one their browser runs on, or they might notice discrepancies in what is displayed in their browser and (for example) generated documents or formatted strings."