How to flatten a PDF: a step-by-step guide

更新日: 2026年10月2日

このガイドはまだ日本語に対応していないため、英語で表示しています。ツール自体は日本語で使えます。

A filled-in form, a contract with reviewers' notes, a document with stamps: what sits on top of the page can look different from one viewer to the next, and anyone can still change it. Flatten PDF draws those layers into the page as they appear, or takes them off, so what you see is what everyone gets. It all happens in your browser; nothing is uploaded.

登録不要で無料でお試しいただけます。ファイルが端末の外に出ることはありません。

PDFフラット化を開く

概要

  1. Drop your PDFs on the page, or press Add files.
  2. Choose what happens to the form fields, the markup and the links.
  3. Check the counts in the file list.
  4. Press Flatten: the file is saved to your device straight away.

Add the files

Drop the PDFs anywhere on the page, or press Add files. Every file is counted as it arrives - the list says how many annotations it carries, the header how many fields, notes and links. Flattening changes nothing you can see: the fields and notes become part of the page they sit on.

Flatten PDF with three files: the reviewed contract with a red box and a sticky note on its first page, 2 notes and 1 link in the header

What happens to what

  • Form fields - Flatten draws each field's current value into the page and removes the form, so it can no longer be filled in or changed; Keep leaves it fillable.
  • Comments, highlights, stamps, drawings - Flatten draws each into the page as it appears, transparency included; Remove takes them all off for a clean copy, as before review; Keep leaves them.
  • Links - Keep (the default: links are navigation, not decoration) or Remove; the text under a link stays.
The three choices: Form fields on Flatten, Comments on Flatten, Links on Keep
A filled-in membership form selected: 8 fields, its typed values to be drawn into the page
A filled-in form: the typed values stay exactly where they are, as part of the page.

Flatten and save

Press Flatten. The line under the button counts the annotations that change. The file is saved to your device at once - several files together as a ZIP; afterwards the list says how many were flattened and removed. A file these choices don't touch produces nothing.

A digitally signed document is flagged: flattening rewrites the file, which breaks the signature. The original stays valid; the output is a plain copy - fine for printing.

Several files at once

Above the file list, Apply to decides how several files are flattened. Under Selected file each file can have its own choices; under All files one set of choices is used for every file. Copy to the other files gives the choices on screen to the other files.

Limits

Without an account, and with a free one, you can flatten two files in a run, each up to 15 MB. With Pro there is no limit on the number or the size, and you can save your choices as a preset.

What next?

さっそく試してみましょう

登録不要で無料でお試しいただけます。ファイルが端末の外に出ることはありません。

PDFフラット化を開く

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