ADVANCED PDF
Free Flatten PDF online
Lock filled-in form fields into the page.
Flatten PDF is a free browser tool that lets you lock filled-in form fields into the page. Drop your PDF into Flatten PDF, choose your settings, and save the finished file. Flatten PDF works on your device only, so no file or text is ever uploaded.
- Free to use
- No signup
- No uploads
- Works offline
Why use Flatten PDF
- lock filled-in form fields into the page without installing software
- Your PDF is processed on your device by Flatten PDF, never uploaded
- Flatten PDF needs no account, email address or payment details
- Flatten PDF is batch-friendly: reuse it immediately on the next file
- Flatten PDF is keyboard accessible and screen-reader friendly
- Flatten PDF is free forever, with no watermark on the result
Flatten PDF runs entirely inside your browser. Your PDF is never uploaded, stored or shared, and nothing is retained once you close the tab.
How to use Flatten PDF
- Add your PDF Drag your PDF onto the drop zone or pick it from your device.
- Adjust the options Set the options that control how Flatten PDF handles your input.
- Run the tool Flatten PDF works instantly on your device, with no queue and no upload wait.
- Download the result Save the finished file straight to your device, then reuse the tool as often as you like.
Benefits
Private by design
Your PDF stays on your device while Flatten PDF works. Flatten PDF never sends it to a server, so confidential work stays confidential.
Instant results
Flatten PDF finishes most jobs in under a second because the work happens on your own hardware.
No signup, no limits
Use Flatten PDF as many times as you want. Flatten PDF asks for no account, adds no watermark and keeps no paid tier gating the output.
Works offline
Once the page has loaded, Flatten PDF keeps working without a connection, which helps on flights and locked-down networks.
Who it is for
For students
Students use Flatten PDF to hand in coursework without installing software: lock filled-in form fields into the page on a shared or locked-down machine.
For freelancers
Flatten PDF helps freelancers send client deliverables quickly, since your PDF never leaves the laptop it was created on.
For HR and admin teams
Flatten PDF helps HR and admin teams process paperwork quickly, since your PDF never leaves the laptop it was created on.
How it works
Flatten PDF loads your PDF into memory, applies the change you requested to the underlying data rather than to a screenshot of it, and writes a fresh copy for download. Your original stays untouched on disk, and every step of Flatten PDF happens inside your browser sandbox.
Frequently asked questions
Is Flatten PDF free to use?
Yes. Flatten PDF is completely free with no account, no trial and no usage cap. Every feature on this page is available on the first visit.
Does Flatten PDF upload your PDF to a server?
No. Flatten PDF processes your PDF inside your browser, so it never reaches a DocTools server. That also means the tool keeps working if your connection drops mid-task.
Is there a file size limit?
The practical ceiling is your device's available memory rather than a server quota. Files up to roughly 100 MB work comfortably on a typical laptop in Flatten PDF.
Do I need to install anything to use Flatten PDF?
No installation is needed. Flatten PDF runs in Chrome, Edge, Firefox and Safari, on desktop and on mobile, with no extension or plugin.
Can I use Flatten PDF on a phone or tablet?
Yes. The Flatten PDF interface adapts to small screens and supports touch input, though very large jobs are faster on a desktop browser.
What happens to your PDF when I close the tab?
It is discarded. Flatten PDF keeps everything in temporary browser memory, so closing the tab removes every trace of the session.
Related tools
- Fill PDF Forms | Detect and fill form fields in PDFs
- Merge PDF | Combine multiple PDFs into one document
- Split PDF | Separate a PDF into individual pages
Last updated: 2026-09-07