Lock a PDF Form So the Answers Cannot Be Changed (Flatten)
Flatten the interactive form fields in a PDF into static page content so the values cannot be edited, cleared, or reverted — 100% in your browser, no upload
Drop a PDF here or click to browse
🔒 Processed in your browser — never uploaded.
Turn a fillable form into a fixed page
A filled-in PDF form stays live: every text box, checkbox, radio button, dropdown and signature field can be re-opened, edited, cleared, or reset by anyone who receives the file. Flattening fuses those fields into the page — each one is drawn at its current value as ordinary page content and the interactive widget is removed — so the document reads and prints exactly as it looks now, while the answers can no longer be changed or reverted. Drop a PDF here, click Flatten form, and download a locked copy; the tool also reports how many fields were flattened, and your original file is left untouched.
Runs in your browser — nothing is uploaded
All processing happens locally with the pdf-lib library, so your PDF never leaves your device and is never sent to a server — safe for signed contracts, applications, and other sensitive paperwork. The page text, images, order and size stay untouched; only the form layer is baked in. One limit worth knowing: flattening makes fields non-editable by design, so keep your original if you might still need to change the answers, and a PDF with no form fields simply comes back as a clean copy.
Frequently asked questions
What does flattening a PDF form do?
It draws every form field — text boxes, checkboxes, radio buttons, dropdowns and signatures — into the page at its current value and then removes the interactive widget. The result looks identical, but the values become static page content that cannot be edited, cleared, or reset in a PDF reader.
Can the fields still be edited or reverted afterwards?
No. Once flattened, the form fields are gone from the document, so there is nothing left to click into or change. Flattening is one-way, so keep your original PDF if you might still need to update the answers later.
Is my PDF uploaded anywhere?
No. Everything runs in your browser with pdf-lib. Your file never leaves your device and nothing is sent to a server, which makes this safe for signed or confidential documents, and it also works offline.