Flatten PDF presses form fields into the page: what you filled in becomes ordinary text and graphics, the fields themselves are removed, and whoever opens the file can read everything but can no longer edit or click anything. It is the “Flatten (fix content)” export mode of the “PDF Forms” panel, available after filling a form, or straight away if you just want to fix the existing values.

Flattening deals with AcroForm fields only and leaves the page's own text, pictures and already-written annotations alone.

1. 01Select a PDF that has a formthe panel lists every field; change values here if you need to, otherwise skip this step.
2. 02Pick the export modeswitch “Export mode” to “Flatten (fix content)”; the note below changes to “Flattening fixes the field values as part of the page and they cannot be edited again”.
3. 03Flatten and downloadclick “Flatten and download” for <original-name>_flattened.pdf and the message “Exported flattened — the content is now fixed”.

Accepted input

unencrypted PDFs with AcroForm fields; a file with no fields needs no flattening

What is affected

only form fields are removed, with their appearance kept; note and link annotations are not touched, and pages are not rasterised (text can still be selected and copied)

Signature fields

fields are removed wholesale, so a digital signature stops being valid once the file is flattened

Chinese

if a field value contains Chinese, a Noto Sans SC font is loaded from this site first to build the appearance (about 10 MB, first time only)

What it does not do

no encryption (use “PDF Protect”), no copy protection for text (convert with “PDF to Image” and back with “Image to PDF” if you need that), and no fixing of annotations into the page (“PDF Annotate” writes flat annotations already)

Flattening happens locally in the browser and the file is not uploaded; a Chinese value triggers a one-off font download from this site.