Hello,
It is not necessary to import the JP language package because it only contains the SAP standard texts. For smartform you have to add your own translation via SE63 for JP version.
You mentioned that the JP characters are displayed in preview so the language key and the
translation might be correct. You should try to use a cascading font device type like SWINCF to see
if the PDF is OK.
Regards,
Wen Peng