If you are using a Slavic or Arabic font, you’ll need to select “Unicode” from the “Language support:” drop-down field on the EXPORT tab for the field map layout.
If not a language issue, then you may be using a font in the PDF form that is not compatible with PRO2PDF. Try changing the PDF form field font to Ariel.
Upload the revised PDF form with the same file name as the existing PDF form to overwrite the existing form so there will be no need to remap the fields.
Let us know if you are able to correct the issue by changing the PDF form field font(s).
We remain at your service.