When you export data with the exportData method of the FormDataIntegration Service, and then import the data using importData, the PDF file size increases dramatically. This problem does not occur if you use the import and export options in Acrobat, or use LiveCycle ES 8.2.1 SP3.
This is a bug in LiveCycle ES2 SP1. Update to LiveCycle ES2 SP2 or later. You can also contact Enterprise Support if you require a patch for LiveCycle ES2 SP1 126.96.36.199.