If you export a batch of labels to PDF, and any of the label data contains diacritics, they are mangled on the label. Exporting to CSV works fine, so this appears to be PDF-specific.
I confirm this bug is existent as described.
I think this is a duplicate to bug 2246: Bug 2246 - Label printing doesn't work with Unicode characters and a general problem with unicode + pdf. *** This bug has been marked as a duplicate of bug 2246 ***