FileCarpenter guide
AcroForm vs XFA: why some PDF forms fill normally and others do not
“Fillable PDF” can describe two very different form technologies. The difference matters when a form works in Acrobat but not in a browser.
AcroForm is the conventional PDF form model
AcroForms use PDF field dictionaries and widget annotations for text boxes, checkboxes, radio groups, buttons and choice fields. Many tax, government and business forms use this model. A form filler can update those real field values and preserve the interactive structure.
XFA is a separate XML-based form technology
XFA can describe dynamic forms whose layout and behavior are driven by XML packets and scripting. Browser PDF engines do not consistently implement XFA, which is why an XFA form may appear interactive in Adobe Acrobat but not in a browser-based viewer.
Why fake overlays are risky
Drawing text visually on top of a form can make the page look filled while leaving the real field empty. For supported AcroForms, FileCarpenter writes the actual field value. For unsupported dynamic XFA behavior, it prefers a clear limitation instead of pretending the visual overlay is equivalent.
Before submitting a government form
Reopen the exported file, verify every field, checkbox, radio selection, total and signature, and follow the receiving agency’s instructions. Some forms rely on Acrobat-specific calculations or validation scripts.