Flatten PDF
Lock form fields, comments, and highlights into the page so they can no longer be edited.
Drop your PDF hereChoose a file to get started
Free tier supports files up to 50MB.
Processed in your browser — files never leave your device
How to Flatten a PDF
A filled-in PDF form looks finished, but under the surface every answer is still an editable field — anyone who opens the file can change a figure, untick a box, or delete a signature line. The same goes for comments, highlights, and stamps added during review. Flattening a PDF merges all of those interactive layers into the page itself, so the document looks exactly the same but can no longer be altered with an ordinary PDF reader. PDFDoco does it in seconds, directly in your browser.
- 1
Upload your PDF
We scan it instantly and show how many form fields and annotations it contains.
- 2
Choose what to flatten
Flatten form fields, annotations, or both — each can be switched on or off.
- 3
Flatten in your browser
Everything visible is merged permanently into the page. Nothing is uploaded.
- 4
Download the final PDF
The result looks the same but can no longer be edited, filled in, or changed.
Instant analysis
See exactly how many fields, comments, highlights, and drawings will be locked in.
Links keep working
Hyperlinks are preserved, so your flattened document stays easy to navigate.
Completely private
Your PDF is processed on your own device and never touches our servers.
Why flatten before you send
Completed tax forms, job applications, rental agreements, and insurance claims are often submitted as fillable PDFs. Flattening them first ensures the recipient sees exactly what you entered, prevents accidental edits when the file is opened in a different app, and avoids the common problem of form answers disappearing or displaying differently on phones and older readers.
Locking in review comments and markup
When a contract, design proof, or manuscript goes through review, comments and highlights live in an annotation layer that some viewers hide and others show. Flattening the annotations bakes the markup into the pages so every reader sees the same feedback, and nobody can quietly remove a note after the fact. It is a simple way to create a permanent record of a review round.
Reliable printing and archiving
Print shops, document management systems, and e-signature platforms sometimes ignore form fields or annotations entirely, which can leave blank spaces where your answers should be. A flattened PDF contains only regular page content, so it prints, archives, and converts consistently everywhere — which is why many organizations require flattened files for long-term storage.
Flattening and security work best together
Flattening stops casual changes, but it does not stop someone from opening the document. For sensitive paperwork, flatten the file first and then add a password with Protect PDF. The result is a document whose contents are both fixed and private.
Pro tip: flattening is permanent. Save your editable original under a different name before flattening, so you can update the form later without starting from scratch.
Frequently Asked Questions
What does flattening a PDF actually do?
Interactive elements such as form fields, comments, highlights, and drawings normally sit in a separate layer on top of the page. Flattening paints their current appearance directly onto the page itself and removes the interactive layer, so what you see becomes a fixed part of the document.
Can a flattened PDF be edited again?
The form fields and annotations can no longer be changed with normal PDF readers, because they no longer exist as separate objects — they are now part of the page content. Keep a copy of the original if you might need to edit the form again later.
Will the text in my form fields still be searchable?
Yes. Filled-in values become regular text on the page, so they remain selectable and searchable, and the overall quality of your document is unchanged.
Why were some annotations not flattened?
A few annotations — often sticky notes created by older software — are stored without a visual appearance, which leaves nothing to paint onto the page. These are left in place and the tool tells you how many there were.
Is flattening the same as making a PDF secure?
Not exactly. Flattening prevents casual changes to form data and comments, but the page itself can still be edited with professional software. To stop people opening the file, combine flattening with a password using Protect PDF.
Does flattening reduce file size?
Sometimes slightly, because interactive form data is removed, but the main purpose is to lock content rather than to compress. Use Compress PDF if you need a significantly smaller file.