Sorry to say that if the custom form code is complex and not the default and basic HTML code, it will be export as PDF properly. This has been the case for a while. There doesn’t seem to be a community demand to change it. I believe exporting and importing data has been largely through APIs and probably many resort to the default forms.
@Gassim, thank you for your message. I believe that most of community members have faced this issue, but hesitate/reluctant to rise the question.
Of course would be great if community members at least show the interest and add their votes so this issue could be revised by the developers more closely.
Additionally there are another problem connected to the options translations in the pivot table, during the export to xls/csv. It is completely disregards translations only during the export, although on the screen everything is completely fine. And as a result I couldn’t get not only translated table, I couldn’t get pivot table as formatted on the screen…
So let’s wait hopefully developers will look at this problem soon.