How to flatten annotations, comments and stamps into a PDF

Updated 19 August 2026

Flattening a PDF merges its annotations — highlights, stamps, ink, sticky-note markers — and its form fields into the fixed page content, so nobody can move, edit or delete them afterwards and every reader shows the same page. UnboundPDF’s Flatten tool bakes each annotation’s own appearance into the page, keeps the page as vector (not an image), names anything it could not bake, and runs in your browser without uploading.

Make comments, highlights, stamps and form fields a permanent part of the page. How flattening works, what it bakes in.

1. Open Flatten PDF and drop in the annotated or filled-in PDF.
2. Run it. The result lists what was baked in, by type, and names anything that was removed instead.
3. Download. Open the file and try to select a highlight or a stamp — it is now part of the page.

What “flatten” means here

Annotations and form fields live as separate objects on top of the page; readers draw them, and readers can also hide, move or delete them. Flattening takes each one’s appearance — the exact graphic the reader would have drawn — and writes it into the page content itself at the same position, then removes the separate object. The page stays vector: text underneath is still text, nothing is rasterised.

Flatten PDF does this in your browser, without uploading the file.

Three exceptions, named

Pop-up note windows are removed rather than baked — they never print, and there is nothing sensible to draw. Hidden annotations (flagged not-to-display) are removed without being drawn, as a reader would treat them. And anything with no appearance stream at all cannot be baked, because there is nothing to bake — the result names each one so you can decide whether that matters.

Stamps, sticky notes, highlights, ink

A DRAFT stamp becomes part of the page. A highlight becomes a fixed translucent band over the words. Ink drawn with a pen or finger becomes a fixed stroke. The sticky-note icon stays where it was; its pop-up window, as above, does not. Transparency and blending are preserved. A DRAFT or CONFIDENTIAL stamp added with the watermark tool is already page content, not an annotation, so it needs no flattening of its own — but flattening the rest of the file locks everything else down around it.

Rotated pages and odd page boxes

Annotations on a rotated page, or on a page whose origin is not the usual bottom-left, land where they were displayed — this is where flattening tools commonly go wrong, and it is tested here on rotated and offset pages.

Forms without fields, fields without forms

A file with form fields and no other markup is flattened. A file with comments but no fields is flattened. Only a file with neither is refused — and it says so rather than producing an identical copy.

Checking the result

Open the flattened file in the PDF Editor or any reader and click a highlight or stamp: nothing should be selectable as an object. Search the page text — still there, because the page was not turned into an image.

What it does not do

It adds nothing. It does not remove markup you want gone — for that, Remove Annotations strips comments and fields instead of baking them. It does not flatten layers (optional content), and it does not redact: a flattened highlight still shows the words under it. To remove words, Redact PDF.

Frequently asked questions

Does flattening turn my PDF into an image?

No. Each annotation’s appearance is written into the page as vector content; the page text stays selectable and searchable.

What happens to sticky notes when I flatten?

The note icon is baked into the page; the pop-up window is removed because it never prints and has no drawable appearance.

Can I flatten just the form fields and keep the comments editable?

Flatten PDF bakes both. To remove comments instead of baking them, use Remove Annotations; to keep them editable, do not flatten that file.

Why does the result name an annotation it removed?

Because it had no appearance stream — nothing to bake — or it was hidden or a pop-up. The result lists each so you can decide whether it mattered.

Is the file uploaded?

No. Flattening happens in your browser; the document never leaves your device.