Flatten PDF Online
Lock filled form fields, signatures and annotations into the page so they can no longer be edited, cleared or reopened in a form editor.
Drop your PDF here to flatten it
or click to browse. Flatten several files at once. Nothing is uploaded.
What does it mean to flatten a PDF?
Flattening a PDF merges everything that sits on top of the page into the page itself. A filled form, a signature, a highlight or a sticky note is not really part of the document until you flatten it. Until then each one is a separate interactive object that a reader can click, edit, clear or delete. Flattening paints those objects permanently into the page content and removes the interactive layer, so what you send is exactly what the other person sees.
This matters most with forms. When you fill in a PDF application, contract or tax form and email it, the values you typed are still live form fields. The recipient can open the file, change a number, and the document will look completely untouched. Flattening closes that gap and is the reason most organisations ask for a flattened copy of a signed document.
This tool flattens in the browser and offers both approaches. Flatten form fields is the precise option, locking filled values into the page while keeping the text selectable and searchable and the file small. Flatten everything to images rebuilds every page as a picture, which strips form fields, annotations, links and the text layer in a single pass when you want nothing interactive left at all.
How to flatten a PDF
- Upload your PDF: Drag the filled form or annotated document into the drop area, or click to browse. You can queue several files and flatten them all with the same settings.
- Choose how to flatten: Flatten form fields locks filled values into the page and keeps the text selectable, which suits almost every case. Flatten everything to images rebuilds the pages as pictures and removes every interactive element including annotations and links.
- Pick an output quality for image mode: If you chose the image option, select a resolution. 150 DPI suits documents that will be read on screen, while 300 DPI is worth the larger file when the document will be printed professionally.
- Flatten the document: Click Flatten PDF. Each file is processed locally in your browser and the tool reports how many form fields it locked into each document.
- Download the flattened file: Download each file individually, or use the download button in the header to get every flattened document at once as a zip archive.
Which flattening mode should you use?
Flatten form fields is the right answer for filled applications, signed contracts, invoices and tax forms. It rewrites the document so the values become ordinary page content, which means the file size barely changes, the text can still be selected, copied and searched, and the pages stay crisp at any zoom level. Screen readers can still read the document, and search engines and document management systems can still index it.
Flatten everything to images is the heavier option, and the one to reach for when a document carries annotation layers, comment threads, stamps, embedded links or anything else you want gone. Because each page is rebuilt from a bitmap, nothing interactive can survive. The trade-offs are real, though: the file gets considerably larger, the text is no longer selectable or searchable, and the document becomes inaccessible to screen readers. Use it deliberately rather than by default.
Flattening is not the same as password protection
It is worth being precise about what flattening does and does not give you. Flattening removes the easy, invisible edit. Once a form is flattened, a recipient cannot simply click a field and retype the amount, and there is no interactive layer left to tamper with. For everyday business documents that is exactly the assurance people are looking for.
What flattening does not do is make a document cryptographically tamper-proof. Someone determined enough, with the right software, can still alter page content in any PDF, flattened or not. If you need to stop a document being opened at all without a password, protect it with encryption. If you need proof that a document has not changed since it was signed, that calls for a certificate-based digital signature rather than flattening. Many workflows use flattening and password protection together: flatten first to lock the content, then encrypt to control who can open it.
When you should flatten a PDF
- Before sending a filled form: so the recipient cannot alter the values you entered.
- After signing a document: so the signature becomes part of the page instead of a moveable object.
- To fix printing problems: some printers and older readers ignore form field contents entirely and print a blank form. Flattening makes the values print reliably everywhere.
- To fix display problems: filled values that appear in one PDF reader but vanish in another are almost always an appearance stream issue that flattening resolves.
- Before merging documents: combining several PDFs that each contain form fields with the same names can cause values to overwrite each other. Flattening first avoids the clash.
- To remove review comments: clearing annotation layers before a document goes to a client or gets archived.
Frequently Asked Questions (FAQs)
Is this flatten PDF tool free?
Yes. It is completely free with no account, no watermark and no limit on file count or page count.
Are my documents uploaded to a server?
No. Flattening runs entirely inside your browser. Your PDF is read from your own disk and the flattened copy is written back locally, so signed contracts and filled forms never leave your device.
Will flattening keep my text selectable?
With the Flatten form fields option, yes. The text stays selectable, searchable and accessible to screen readers because the page is still built from real text. The Flatten everything to images option rebuilds each page as a picture, which does remove the text layer.
Can a flattened PDF be edited again?
The form fields are gone, so nobody can click into them and change a value. The page content itself can still be altered by someone using professional PDF editing software, because that is true of any PDF. Flattening prevents casual and accidental edits rather than providing cryptographic protection.
Does flattening remove comments and highlights?
The Flatten form fields option focuses on form field widgets and leaves separate annotation layers in place. If you need comments, highlights and sticky notes gone as well, use Flatten everything to images, which removes every layer that is not part of the page picture.
Why did the tool say no form fields were found?
That means the PDF has no interactive form to lock down, which is normal for documents exported straight from Word or a design tool. The file is still processed and saved, and if your goal was to remove annotations or the text layer you should switch to the image option.
Does flattening make the file bigger or smaller?
Flattening form fields usually changes the size very little, and often makes the file slightly smaller because the interactive form structure is removed. Flattening to images almost always makes the file larger, since page text is replaced by full-page bitmaps.
My filled form prints blank. Will this fix it?
Yes, this is one of the most common reasons people flatten a PDF. Some printers and readers do not render form field contents. Once the values are flattened into the page they are ordinary page content and will print from anything.
Can I flatten a password protected PDF?
Not directly. An encrypted PDF has to be unlocked before any tool can modify it. Remove the password first with our Unlock PDF tool, flatten the document, and then re-protect it if you still need it encrypted.
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