Lock a PDF Form So the Answers Cannot Be Changed (Flatten)
Fuse a PDF's filled form fields into ordinary page content so the values can no longer be edited, cleared or reset by whoever opens the file next.
🔒 Form field values are fused into the page in your browser — the PDF is never uploaded, before or after flattening.
Drop a PDF here or click to choose
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 Lock the answers in, 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. Comments, highlights, stamps and drawings stay editable unless you tick Also burn in comments, highlights, stamps and drawings (off by default), which draws each visible one into the page as it looks and removes it as a separate note; links are left alone, and one with no drawing of its own is left editable and counted in the report. One limit worth knowing: flattening makes fields non-editable by design, so keep your original if you might still need to change the answers. A PDF with no form fields 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. pdf-lib draws each field's current value into its page and saves the result in this tab. An answer in Hangul makes it fetch a Korean font from this site; the PDF itself goes nowhere.
Can it lock comments, highlights and drawings too, not only form fields?
Yes, if you ask. Tick “Also burn in comments, highlights, stamps and drawings” before pressing “Lock the answers in”, and each visible one is drawn into the page exactly as it looks and removed as a separate note, so it can no longer be edited or deleted on its own. It is off by default, so a plain flatten keeps a reader’s notes as they were. Links keep working, hidden notes are left alone, and a note with no drawing of its own stays editable — the result says how many were burned in and how many were left.