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Flatten PDF
Flatten PDF converts interactive AcroForm fields into permanent page content, so a filled-in form looks the same everywhere and can no longer be edited or reset. If a document has no form fields, the tool reports that honestly and leaves the content unchanged.
How to use Flatten PDF
- Upload the filled PDF form.
- Run the flatten pass, which fixes every field value onto its page.
- Download the flattened document and confirm the values are visible.
Where Flatten PDF is useful
- Locking a completed application form before submitting it.
- Preventing a client from accidentally clearing field values.
- Producing a printable version of a form whose widgets misrender in some viewers.
Formats, algorithms and limits
pdf-lib's form-flattening routine draws each field's appearance stream onto the page and removes the interactive widget. Comments and highlights that live in a separate annotation layer are not turned into page pixels by this pass, so treat it as form flattening rather than full artwork flattening.
Troubleshooting and honest limits
- Fill the form first — flattening an empty form removes the ability to type into it.
- Check that every field shows its value on the flattened page; date pickers and signature fields occasionally render blank in broken forms.
- Keep the unflattened copy if you may need to revise the entry later.
Frequently asked questions
What exactly is flattened?
Interactive AcroForm fields: text boxes, checkboxes, radio buttons and dropdowns. Their current values become fixed page content and the widgets are removed.
Will my annotations and comments also be flattened?
No. This pass targets form fields. Comments remain a separate annotation layer, which is why some readers can still hide or edit them.
Can I undo flattening?
Not in the output file — the field data is replaced by drawn content. Keep the original for future edits and flatten only the copy you are distributing.
The tool said there are no fields. Why?
The document is a static PDF with no interactive form layer, so there is nothing to flatten and the content is left as it is.
Related tools
Page written and reviewed by the FreeConvertio engineering team on 2026-10-14. Flatten PDF runs entirely in your browser — no uploads, no account and no daily limits.