It seems that since the December update the "Export to PDF" is buggy and the actual report area is surrounded by white margins on all sides. page size (for all pages): 16:9 Fit to size activated...
Thanks a lot for your help. The issue is only in the PowerBI service. Desktop works fine. And yesterday found a workaround. The issue occurs only when I have a Image in Background set a "Fit" in Image Fit property. When I changed to Fill, it works, but the Dashboard was working very well all the year with this configuration. Looks like something change this month in the service.