Flatten PDF — Lock Form Fields and Annotations
Merge form fields and annotations into the underlying page so recipients can no longer edit them. The result is a stable, print-ready PDF that looks identical in every viewer.
Flatten PDF
Merge form fields and annotations into the page
About the Flatten PDF tool
Flattening is essential after signing or filling forms, especially when the file will pass through email clients or archival systems that may not render live form data correctly.
Because the flatten runs in-browser, sensitive filled-out forms stay private throughout.
Key features of Flatten PDF
- Locks form fields and annotations
- Ensures consistent rendering across viewers
- Preserves visible text and images exactly
- Runs 100% in the browser
- Free and unlimited
How to use Flatten PDF
- Upload a filled form or annotated PDF.
- Click ‘Flatten PDF’.
- Download the locked-down file.
Common use cases
- Lock a filled tax form before emailing
- Freeze signatures on contracts
- Prepare archival copies of official forms
- Prevent recipients from editing shared PDFs
- Ensure consistent print output
Frequently asked questions
Can I unflatten a PDF later?
No — flattening is a one-way operation. Keep an editable copy of the source form if you might need to change it.
Do links and bookmarks still work after flattening?
Yes. Only form fields and annotations are merged into the page; navigation links remain functional.
Is this tool safe to use with confidential files?
Yes. Every file is processed locally inside your web browser using JavaScript and WebAssembly. Nothing is uploaded to a server, stored, or shared — so contracts, invoices, medical records and personal documents stay 100% private on your device.
Is it really free? Are there any limits or watermarks?
Yes, it's completely free with no sign-up, no daily limits, and no watermarks stamped on your output. Process a single file or hundreds — the only limit is your device's memory.