2026-10-03

A Flatten PDF Tool That Works in Your Browser (Form Fields and Annotations, No Upload)

Searching for a way to flatten a PDF turns up online services that ask you to upload the file. That is a poor fit for the files people usually flatten: a filled-in application, a signed-off contract or a form full of personal details. The Flatten PDF tool does it in your browser tab, so the document is never sent anywhere.

What it does

• Flattens form fields. Text boxes, checkboxes, radio buttons and dropdowns become fixed content on the page, so the answers cannot be changed and look the same in every viewer.
• Optionally flattens annotations. Highlights, ink drawings, shapes, stamps and free-text boxes that have a stored appearance are drawn into the page and removed as annotations.
• Tells you what it did. The summary lists how many fields and annotations were flattened, how many links were kept clickable, and how many annotations had no appearance and were left alone.
• Warns about the awkward cases. XFA forms, which this approach cannot flatten, are flagged before you run it.

What it does not do

Flattening is one-way, so keep the original. The words of a comment are not kept once the comment is flattened, only its drawn look. Digital signatures stop validating after the file is saved, so do not flatten a document that has to stay signed. Links stay as links, and an annotation that has no stored appearance is left as it is. The tool does not make text unselectable or remove hidden content; for that, see Compress PDF with page rasterising.

When another tool is the better fit

Filling a blank form. Fill PDF Forms lets you type into the fields and saves the result already flattened, so for a blank form that one step is enough.

Signing. To add a signature image to a finished document use Sign PDF.

Printing to PDF. Printing a document to PDF from a viewer or operating system can also flatten it, but links, bookmarks and tags may be lost and the results vary by viewer, so check the output.

Desktop editors. Acrobat and other desktop PDF editors have their own flatten and redaction features with more control over individual items.

Verdict

To lock in a filled-in form, or burn highlights and drawings into a PDF, without uploading it anywhere, try Flatten PDF. Keep the original, and check the result if the file uses XFA.

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