Flatten PDF

Flatten form fields into static content

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What is Flatten PDF?

Flatten PDF is a free online tool that permanently merges interactive form fields, annotations, comments, and layered content into the base page of your PDF. After flattening, all elements become part of the static page content and can no longer be edited, moved, or deleted. This is essential when you need to lock in the current state of a document for archiving, submission, or distribution. The tool uses the pdf-lib JavaScript library and runs entirely in your browser. Your file is never uploaded to any server, keeping filled-in tax forms, signed contracts, and annotated reports completely private.

When to Use Flatten PDF

Use this tool whenever you need to lock the contents of a PDF so that form fields and annotations cannot be altered. Common scenarios include:

  • Submitting a filled-in government or insurance form that must not be editable after signing.
  • Archiving annotated contracts or agreements so comments become permanent.
  • Preparing a document for print where interactive elements could cause rendering issues.
  • Locking down a graded exam or reviewed manuscript before returning it to the author.
  • Reducing file complexity by collapsing layers, which can also decrease file size.

How It Works

Upload your PDF by dragging it into the drop zone or using the file picker. The tool reads the document within your browser, identifies all interactive form fields, annotations, and layered objects, and merges them into the static page content using pdf-lib. The resulting flattened PDF is then available for immediate download. Because the entire process happens client-side in JavaScript, it works offline once the page has loaded, requires no account creation, adds no watermark, and is completely free to use.