What is Flatten PDF and how does it work?

Flatten PDF is a free online tool from HuntPDF. Flatten PDF form fields and annotations into static, non-editable content. You upload a file, the work happens on our servers, and you download the result. There is nothing to install and no account to create.

How do I use Flatten PDF online?

Upload your file using the box above — drag it in, browse for it, or bring it in from your cloud storage. A preview appears so you can check you've picked the right file. Run Flatten PDF, then download the result. You can rename it before you save it.

Is my file secure when I use Flatten PDF?

Yes. The file you send to Flatten PDF travels over an encrypted HTTPS connection and is processed automatically on our servers. It is never made public, never shared with anyone, and nobody reads it.

Does HuntPDF store my files after Flatten PDF has run?

No. Your upload is deleted the moment Flatten PDF finishes with it, and the file it produces is removed as soon as you have downloaded it, or when you upload another file, or when you close the page. Nothing is kept, and nothing is used to train anything.

Will the original quality and formatting be maintained?

Yes. Flatten PDF is built to leave your content exactly as it is — only the change you asked for is applied. Nothing else about the file is altered or re-compressed.

Can I use Flatten PDF on mobile?

Yes. Flatten PDF works in any modern browser on phones and tablets — iPhone, iPad or Android — with nothing to install. You can upload straight from your device or from your cloud storage.

Can I rename my file before downloading it from Flatten PDF?

Yes. The file Flatten PDF gives you back keeps the name of the file you uploaded by default. If you'd rather call it something else, edit the name in the field next to the download button before you save it.

Do I need to install any software to use Flatten PDF?

No. There is nothing to download, install or sign up for — Flatten PDF is used from your browser and does the work on our servers, so it behaves the same on Windows, macOS, Linux, Android and iOS.

How long does Flatten PDF take?

Most files are finished in a few seconds. A large or page-heavy file takes a little longer, because Flatten PDF runs on our servers rather than on your device — but you won't be waiting around. You can upload files up to 250MB.

Is Flatten PDF free to use?

Yes. Flatten PDF is free, with no signup, no watermark on the result and no daily limit for normal use.

What does Flatten PDF do?

It turns form fields, comments and other mark-up into a fixed part of each page, so nothing can be edited or removed afterwards.

Why would I flatten a PDF?

To lock a filled form or annotations before sending, and to make the file display the same in every PDF reader.

Can I still read everything after I flatten a PDF?

Yes. Everything stays visible exactly as before. It just can't be changed.

Can I undo flattening?

Not in the flattened file. Keep the original if you might need to change the answers.

How do I know if my file needs Flatten PDF?

Add it and read the note. It lists the form fields and comments found, or says there's nothing to flatten.

Should I flatten before or after signing?

After. Fill in the form, sign it, then flatten so the signature and answers are fixed together.

Flatten PDF Online – Free, No Watermark, No Signup

Drop your file on the target

Several files · up to 260 MB each · deleted after processing

Drop your file here

Choose file

Locks form answers, comments and stamps into the page
Up to 260 MB per file

Processed on our secure servers over HTTPS. Your files are deleted automatically after processing.

Flatten PDF merges form answers, comments, highlights and stamps into the page itself, so they look the same but can no longer be changed, moved or deleted. It's the last step before sending a completed form or a marked-up document.

How to use Flatten PDF

Drop the PDF on the page or choose it from Google Drive, Dropbox or OneDrive. The tool counts what it found, for example '12 form fields and 3 comments', so you know what will be locked in. Press Flatten PDF, then download the file, rename it, or send it on WhatsApp. Use 'Continue with this file' to compress or sign it next.

When to use Flatten PDF

An applicant flattens a completed benefits form so answers can't be altered once it's submitted. A reviewer flattens a marked-up drawing so the site team sees the comments exactly as placed. An accountant flattens a filled tax form that displays differently in some PDF readers.

What flattening changes

Form fields, comments, highlights and stamps become part of the page. The document looks the same, but fields no longer accept typing and comments can't be moved or removed. If the tool finds no form fields or comments, it tells you that flattening won't change how the PDF looks, which saves a pointless step. Keep an unflattened copy if you might need to edit the answers later.

Frequently asked questions

What does Flatten PDF do?: It turns form fields, comments and other mark-up into a fixed part of each page, so nothing can be edited or removed afterwards.
Why would I flatten a PDF?: To lock a filled form or annotations before sending, and to make the file display the same in every PDF reader.
Can I still read everything after I flatten a PDF?: Yes. Everything stays visible exactly as before. It just can't be changed.
Can I undo flattening?: Not in the flattened file. Keep the original if you might need to change the answers.
How do I know if my file needs Flatten PDF?: Add it and read the note. It lists the form fields and comments found, or says there's nothing to flatten.
Should I flatten before or after signing?: After. Fill in the form, sign it, then flatten so the signature and answers are fixed together.