How to flatten a PDF, and when you should
Checked against our tools on 17 October 2026
Flattening a PDF turns its form answers, comments and stamps into part of the page, so they look the same but can't be typed over, ticked, moved or deleted. Open Flatten PDF, add the file, keep both boxes ticked and download the flattened copy. It runs in your browser, so the file isn't uploaded. Keep the original, because flattening can't be undone.
Go straight to the tool: Flatten PDF, Fill PDF forms, Sign PDF
What flattening actually changes
A fillable PDF has two layers: the page itself, and on top of it a layer of interactive things. Form fields hold your answers, and annotations hold highlights, sticky notes, stamps and some signature images. Anyone with a PDF editor, or just a browser, can change that top layer.
Flattening draws each of those things into the page exactly as it appears, then deletes the interactive version. In our test, a form with a filled-in name field and a ticked checkbox had 2 fields before and 0 after. The name still read "Jane Citizen" on the page and could still be selected as text, but there was no box left to type into.
When to flatten
- Before sending a completed form, so the recipient sees exactly what you entered and can't change it by accident.
- After adding a drawn signature, if it sits on the page as an annotation, so it can't be dragged off or deleted.
- When a printer, phone viewer or upload portal shows blank fields. Some don't display form fields or comments at all, but they always show the page.
- When an office asks for a "flattened" or "non-editable" PDF.
The steps
- Fill in the form and add any signature first. Fill PDF form and Sign PDF both run in your browser.
- Open Flatten PDF and add the file.
- Choose what to flatten: form fields, comments and annotations, or both. Both is the usual choice.
- Download the flattened copy. The result screen says how many fields and annotations were flattened.
What's kept and what goes
| Item | After flattening |
|---|---|
| Typed answers, ticks, chosen options | Drawn on the page, no longer editable |
| Highlights, stamps, note icons, boxes | Drawn on the page |
| Text inside pop-up comments | Removed |
| Links | Still clickable |
| Hidden fields and annotations | Removed without being drawn, as viewers already hide them |
| Digital signatures | No longer valid, because the file is rewritten |
What flattening doesn't do
It isn't redaction. Flattening keeps everything visible on the page, and the text of form answers can still be copied. If you need to remove information, use Redact PDF, which rebuilds each marked page as an image with the boxed areas painted black, so the hidden text can't be recovered.
It isn't protection either. Someone determined can still edit the page with a full PDF editor; flattening just removes the easy way. If the recipient must be able to prove nothing changed, add a digital signature after flattening, not before.
Other ways to flatten
Printing to PDF flattens too, because it rebuilds the file from a printout. It also drops bookmarks and document properties, and some printer drivers turn each page into a picture, which makes text unsearchable and the file larger. Adobe Acrobat can flatten with its paid tools. Flatten PDF changes only the fields and annotations and leaves the rest of the file as it was.