What Flatten PDF does
PDFGrover's Flatten PDF tool takes a PDF with editable elements — form field values, annotations, layered content — and produces a new PDF where all of it is baked into the page. It looks identical but can no longer be edited or removed.
When to flatten a PDF
- Locking a filled form so a recipient can't change your answers.
- Finalising a signed or annotated document before sending it on.
- Archiving where the markup is the authoritative record and must not be editable later.
- Consistent rendering across readers that display form fields slightly differently.
- Before e-signature — some platforms require a flat PDF.
How to flatten a PDF
- Upload a PDF (up to 100 MB) — it stays on your device.
- Click Flatten — current form values, annotations, and layer content are merged into the page content.
- Download the flattened PDF — no editable fields remain.
What gets flattened
- Form field values — typed answers become permanent page text; the interactive fields are removed.
- Annotations — comments, highlights, stamps, and free-text overlays become permanent page content.
- Optional layers — any layered (OCG) content is rendered in its current visible state.
Side effects to know
- Interactivity is gone — recipients can't change field values after flattening. If they need to, don't flatten (or send the fillable copy too).
- File size barely changes — usually neutral; slightly smaller if form objects are removed, slightly larger if many annotations are rendered in.
Flatten vs related tools
| Need | Use |
|---|---|
| Lock filled-form answers | Flatten PDF (this tool) |
| Fill the form first | Fill PDF Forms |
| Password-protect the file | Protect PDF |
| Truly remove sensitive data | Redact PDF |
Privacy and file handling
Flatten PDF runs entirely in your browser — nothing is uploaded, stored, or logged. The flattened file exists only in your tab until you download it. No sign-up, no watermark.
Troubleshooting
- Recipient can't fill the form now — that's expected after flattening; send them the un-flattened copy if they need to edit.
- Annotation disappeared — only visible annotations are baked in; hidden/closed note pop-ups may not render — open/expand them first.
- Need the data truly gone, not just locked — flattening keeps the content visible; use Redact PDF for removal.