Flatten PDF form fields
Bake the current appearance of standard form fields into the pages and remove the interactive fields. Your filled copy stays on your device.
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From editable controls to page content
A standard PDF form stores fields separately from the page drawing. Flattening updates their visible appearances, copies those appearances into the pages, and removes the interactive field objects. The result opens with the current answers visible but no editable text boxes, checkboxes, radio buttons or dropdowns.
This is useful for a review copy or an archive snapshot. It is not a substitute for keeping the editable original when answers may need correction later.
AcroForm only, not every kind of “PDF form”
The operation supports standard AcroForm fields that pdf-lib can render. Dynamic XFA forms use a different technology and are refused with a clear error. A PDF with no standard fields is also reported rather than being presented as a successful flatten.
Flattening rewrites the document and can invalidate digital signatures. Scripts, unusual viewer-specific behaviours and external workflows should be tested in the software that will receive the final file.
Questions
+ Can the answers be edited after flattening?
Not as form fields. They become page content. Keep the original file if you may need to change the answers later.
+ Does this support XFA forms?
No. Dynamic XFA forms are detected and refused because pdf-lib cannot reliably flatten them. Convert the form to a standard AcroForm in a suitable PDF application first.
+ What happens if the PDF has no fields?
The row says that no standard AcroForm fields were found. It does not create an identical download and call that a successful flatten.
+ Will signatures remain valid?
No. Flattening changes the document bytes and field structure, so an existing digital signature should be assumed invalidated.
+ Are my files uploaded anywhere?
No. The PDF is read and rewritten by your own browser. Open devtools, watch the Network tab while you run it, and nothing leaves. The page keeps working with your connection switched off, which is the part worth caring about when the document is a payslip, a contract or a medical letter.