That message is a bit misleading since all check boxes have export values. The default is the string "Yes", but you can set it to whatever you want. For some reason, when you have multiple check boxes with the same name and export value, FormsCentral modifies the form when it enables it so that they are not all checked at the same time when any are selected. This is different than the normal behavior for a PDF form and I'm not aware of a workaround. I consider it to be a bug.
I have the same problem:
FormsCentral has successfully imported the PDF with the following exceptions:
The checkbox field 10000 contains an export value. FormsCentral will record the checked state, but will not include the export value.
The checkbox field DATA CENTRE contains an export value. FormsCentral will record the checked state, but will not include the export value.
How to solve? Do you send the form to email@example.com?
Any ideas to solve?