When you add a highlight, a note or a signature to a PDF, it is stored as a separate object on top of the page. Anyone who opens the file in a PDF editor can select that object and delete it.
Flattening merges those objects into the page. The document looks the same afterwards, but there is nothing left on top to select.
The short answer
Open the PDF in OpenPdfEdit, switch to Annotate, choose Flatten, confirm, and save a copy. It runs in your browser tab. The file is not uploaded, and you do not need an account.
When you need to flatten
- You are sending a marked-up document. Your highlights and comments should arrive as you left them, and the next person should not be able to remove one.
- You have signed it. A signature you draw onto a page is stored the same way as a pen stroke. Until you flatten, it is still a separate object.
- You are printing or submitting it. Whether comments are printed depends on the reader and its print settings, and some upload systems, court e-filing for example, ask for a flattened PDF. Once flattened, the markup is part of the page and goes wherever the page goes.
Step by step
- Open openpdfedit.com/app and choose Open PDF….
- Switch to Annotate at the top of the window. If the document still needs markup or a signature, add it now. There is more about the tools in annotating a PDF.
- In the toolbar, choose Flatten. It is in the Markup group, and also under All tools.
- The app tells you what is about to happen: "Markup becomes part of the page. Afterwards it can't be edited, moved or removed." Choose Flatten markup.
- A message confirms how many items were flattened.
- Choose Save a copy. The copy is offered under the same file name as the original, so change the name if you want to keep both. Adding
-flatis enough.
There is nothing to set up. One click flattens the markup on every page.
Flattening a form you have filled in
Form fields are separate objects too. When the PDF has them, the same steps apply and two things on screen change. The message reads "Markup and filled-in form values become part of the page. Afterwards they can't be edited, moved or removed, and the form can't be filled in again." The button reads Flatten markup and fields.
What you typed and the boxes you ticked become ordinary content on the page. Every field is removed, including the ones you left empty, so nobody can type into the form afterwards. Check your answers first, and keep the unflattened copy in case one of them needs to change.
Keep the original
While the document is still open, you can reverse the flattening with the Undo button in the top bar, or with Ctrl+Z on Windows.
Once you have saved the flattened copy and closed it, Undo is gone. Open that copy again and the markup is simply part of the page. If you may need to change a comment later, keep the unflattened original and send the flattened copy.
How to check that it worked
Open the flattened copy and try these checks.
- Switch to Annotate and open Comments. Before flattening, this panel lists every piece of markup, one line each. Afterwards it says "No annotations yet."
- Choose Select and click a shape you drew. Before flattening, the app offers to delete it. Afterwards nothing happens, because there is no longer an object there to click.
- Put it next to the original. The page count is the same, the markup is where you left it, and the text can still be searched and copied.
What flattening does not do
Flattening does not take anything out of the document. Text under a highlight or a strikeout is still in the file, and can still be found by search and copied. If you need to remove information, that is a different job: see how to redact a PDF.
Links in the document are left alone and keep working.
Your file stays on your computer
OpenPdfEdit does the work inside the browser tab. The PDF is read from your disk and the flattened copy is written back to it. Nothing is uploaded.
It also works without a connection. Open the app once while you are online. After that you can reload the page with the network off and flatten as usual.
Printing to PDF
Another route is to open the document in a PDF reader, choose Print, and pick "Save as PDF" or "Microsoft Print to PDF" as the printer. This makes a new file from what the pages look like, which also fixes markup in place. Check the result before you rely on it, because links and bookmarks may not come through.
FAQ
What does it mean to flatten a PDF?
Markup such as highlights, notes and drawn signatures is stored as separate objects on top of the page. Flattening draws them into the page itself, so they can no longer be selected or deleted on their own.
Can I undo flattening?
Yes, while the document is still open: use Undo. After you have saved a flattened copy and closed it, Undo is no longer available, so keep the original.
Does flattening change how the PDF looks?
No. The markup stays where it was. The page count does not change, and the text can still be searched and copied.
Are my files uploaded when I flatten them?
No. The file is read and flattened inside the browser tab, and the copy is saved straight to your computer.
Does flattening cost anything or need an account?
No. Flattening is free and works without signing in.
Can I flatten a PDF offline?
Yes. Open OpenPdfEdit once while you are online. After that it works with the network switched off.