Lock your filled PDF form so fields can't be edited. Bakes form data into the page — no upload, 100% private, free.
Just filled a tax form, contract, or government application? Flatten it before sharing. Flattening permanently merges all form fields, annotations, and overlays into the page — the recipient gets a clean, uneditable PDF that looks exactly as you filled it. Everything runs in your browser: no upload, no account, no install required.
Flatten a filled PDF free: works with AcroForm fields, signature images, checkboxes, stamps, and drawing annotations. Compatible with PDFs from any source — including ones filled with the Fill PDF tool.
Click Choose files or drag your filled PDF into the drop zone. Any PDF with form fields, interactive elements or annotations works — including ones you just filled with the Fill PDF tool.
Press the Flatten PDF button. The tool processes your document entirely in your browser using pdf-lib — converting all interactive fields into static page content in seconds.
Your flattened PDF downloads directly to your device. Open it in any PDF viewer and you will see the content is now fixed — no fields to edit, no checkboxes to toggle, no signature pads to clear.
Once you have filled in your tax form, government application or contract, flattening ensures the recipient cannot alter the values. The form data becomes part of the page — uneditable and permanent.
Interactive form fields sometimes render differently across PDF readers. A flattened PDF looks identical in every viewer — macOS Preview, Chrome's built-in PDF viewer, mobile apps — because it contains only static content.
Some print services and archiving systems expect flat PDFs without interactive layers. Flattening removes all form metadata, widgets and JavaScript — leaving a clean, universally compatible document.
PDF form fields store their values as structured metadata. If you share a filled form without flattening, a recipient could inspect the raw PDF and see field names, original values, or metadata attached to the form object. Flattening removes all of that.
Flattening is the right step whenever you share a filled document that must not be changed by the recipient. The most frequent use cases:
Every step of the flatten operation runs inside your browser using pdf-lib, a battle-tested open-source library. Your PDF — with all the sensitive form data it contains — never reaches any server. Not PDFree's servers, not any third-party service.
This is especially important for forms containing personal or financial data: tax returns, insurance claims, medical records, contracts. You can flatten these with confidence that the data stays on your device.
| Method | Processes locally | No install needed | Free |
|---|---|---|---|
| PDFree (this tool) | Yes — in-browser | Yes | Free forever |
| Desktop PDF software | Yes (desktop) | Requires install | Paid subscription |
| Online cloud tools | No — uploads to server | Yes | Often limited |
| Print to PDF | Yes | Yes (built-in) | Free but lossy |
Flattening merges all interactive layers — form fields, annotations, digital signatures, and overlays — into the static page content. The result is a flat, non-interactive PDF that looks identical to the original but cannot be edited.
No. Flattening is irreversible — the original form fields are permanently replaced by static visual content. Always keep a backup of your original filled PDF before flattening if you think you might need to change values later.
Drawn signatures created with the Fill PDF tool (signature pad images) are flattened into the page. Cryptographic digital signatures from certified e-signature providers may be handled differently — the visual appearance is preserved but the cryptographic certificate may no longer validate after flattening.
No. Everything runs in your browser using pdf-lib. Neither your original PDF nor the flattened result is ever sent anywhere. Your document and its contents stay on your device at all times.
A saved filled PDF still contains editable fields — a recipient could clear your values and re-fill them. Flattening permanently locks the content into the page, prevents editing, ensures consistent rendering across all PDF viewers, and removes hidden form metadata from the file.
PDFree Flatten runs in any modern browser — Chrome, Safari, Firefox, Edge — on Mac, Windows, and Linux. No download or installation required. Open the Flatten PDF tool, load your PDF, click Flatten, and the result downloads directly to your device. No desktop software needed at any step.
Often slightly. Flattening removes interactive form widget data and JavaScript, which reduces file size for forms with many fields. However, images and embedded fonts are unaffected. For significant size reduction, run the flattened output through the Compress PDF tool.
They solve different problems. Flattening removes the interactive form structure entirely — no fields exist to edit, regardless of permissions. Password protection restricts access or editing rights but leaves form fields intact; someone with the password could still modify a fillable form. For maximum security, flatten first to bake the content, then add a password with Protect PDF.