Open Writer empty document and go to "Iools > Options > OpenOffice
Writer > Basic font (Western) " and on the card select the type and size
of font you want to make default, set it properly and confirm.
Currenly I use OpenOffice version 4.1.6 and this procedure is adequate
to this version, but I remember that in the earlier version of OO (v.3.1
I used) in the program settings there was also a separate option to set
the default western and Asian font
(which I have not noticed in the current version). After setting the
smaller font size, each new document will be automatically created with
this size, while documents that have a larger font size will have to be
separately. Edit and format to the new Writer default settings.
Maybe someone more familiar with the topic will advise you something
Meanwhile, I greet and wish you peace and creativity in solving the