Flatten PDF: how it works
To flatten a PDF, open the Flatten PDF tool and add your file; PDFER bakes interactive form fields and annotations into the page so they can no longer be edited, then downloads the flattened PDF. Everything happens in your browser.
How to use Flatten PDF
- Open the Flatten PDF tool and add your PDF.
- Let PDFER merge form fields and annotations into the page content.
- Download the flattened PDF.
In your browser vs. uploading to a server
Best for finalizing a filled form so the answers are permanent and display identically everywhere.
Frequently asked questions
What does flattening a PDF do?
- Flattening merges form fields, annotations, and layers into the static page, so the content can't be edited or accidentally changed and renders the same in every viewer.
Are my files uploaded to a server?
- No. PDFER runs entirely in your browser using WebAssembly and JavaScript. Your files are read into memory on your device, processed locally, and never sent to PDFER or any third party. Closing the tab or leaving the tool erases them from memory.
PDFER is a privacy-first PDF toolkit built by Kiril Urbonas. Every tool runs entirely in your browser — see our security model and privacy policy.