Flatten a PDF

1 min read·23 July 2026

Do you have a PDF with form fields, signatures or annotations that you want to lock in place? Flattening makes those elements part of the fixed page content so they can no longer be changed.

What does flattening a PDF mean?

Annotations, form fields and digital signatures are "layers" on top of the PDF content. They are editable and can be removed. Flattening merges all layers with the page so the result is one unchangeable image per page.

When do you use flatten?

You fill in a form and want to prevent the recipient from changing the fields. You have made annotations you want to lock. Or you want to prepare a PDF for printing where all elements are in exactly the right place.

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Can I still make changes after flattening?

No. Flattening is irreversible. Always keep the original version before flattening. After flattening, form fields can no longer be filled in, signatures are no longer valid as digital signatures (still visible) and annotations are removed as a layer.

Difference from printing to PDF?

Printing to PDF gives a similar result but via the printer driver. Flatten works directly on the PDF structure, keeping file size smaller and preserving the vector quality of text.