Flatten PDF
Lock form fields into the page so answers can't be changed — flattened in your browser.
Best for: Reach for the Flatten PDF whenever you need a fast, accurate flatten pdf — for flatten pdf, lock pdf form, make pdf uneditable and similar tasks.
Purpose: Lock form fields into the page so answers can't be changed — flattened in your browser.
Input
How it's calculated & sources
Method: pdf-lib draws every form field's current value directly into the page content and removes the interactive field — the standard way to make filled forms final. Runs entirely in your browser; nothing is uploaded.
Free & no sign-up · runs entirely in your browser. Results are estimates for general information, not professional advice — verify important decisions with a qualified expert. Last reviewed June 2026.
Frequently asked questions
When should I flatten a PDF?+
Before submitting or archiving a filled form: flattening stops recipients (and other PDF apps) from editing or accidentally clearing your answers.
Does it flatten annotations and signatures too?+
It flattens AcroForm fields — text boxes, checkboxes, dropdowns, radio groups. Sticky-note annotations are a different layer and are left untouched.
Can flattening be undone?+
No — that's the point. Keep your original if you might need to edit the answers later.
Is my document uploaded?+
No. The whole operation runs in your browser. No byte of your PDF is sent anywhere.
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