How to flatten a PDF with OnyxPDF
- Drop the filled PDF into the tool.
- Click “Flatten PDF”.
- Download the flattened copy — fields are now part of the page.
Why do it in your browser instead of uploading?
- The completed form looks identical everywhere — no reader can render your answers differently or drop them.
- No upload: flatten a filled application or agreement locally.
- Free — flattening sits behind Pro tiers at several big sites.
- The standard final step before emailing a completed form to anyone.
Good to know (honest limits)
- Flattening is one-way: afterwards the fields cannot be edited or refilled. Keep an unflattened copy if changes are likely.
- Annotation flattening is partial — form fields are fully baked; some exotic annotation types may remain as objects.
Frequently asked questions
Why flatten a PDF?
To freeze a filled form: the values become part of the page, so they cannot be changed, lost or rendered inconsistently by different PDF readers.
Can I still edit the form after flattening?
No. That is the point of flattening. Always keep the unflattened original if you might need revisions.
Does flattening change how the form looks?
No — the values stay exactly where they were; only their editability is removed.
Is my file uploaded?
No. Flattening happens in your browser with pdf-lib.