Flattening makes filled forms and markups a permanent part of each page.
How to flatten a PDF
- Add your filled form or annotated PDF to the panel.
- Click the button to flatten it.
- Download the new PDF with forms and markups fixed into the pages.
When to flatten a PDF
Flattening locks in what you see: filled form values and annotations become a permanent part of each page, so they display identically in every viewer and cannot be changed or lost.
It is the standard final step before sending a filled form, because some systems mis-render live form fields, and recipients on different apps may see different states.
Why flatten PDFs in your browser
The operation runs locally, so your filled document never leaves your device. No upload, no account, no risk of a third party seeing the data.
Free in any browser; the PDF Shrink iPhone app offers the same local tools offline.
FAQ
Why flatten a PDF?
Flattening locks in filled form values and annotations so they display the same everywhere and can't be changed.
Can I undo a flatten?
No. Flattening is permanent by design. Keep the original file if you may need to edit the form again.
Does flattening reduce file size?
Often slightly, since interactive form structures are replaced by static content.
Is the original file changed?
No. The flattened result is a new file; your original stays untouched.