Is flattening the same as “Print to PDF”?

The result is similar for form fields and comments, but printing to PDF also rebuilds the whole file: links and bookmarks are lost, and text may be affected. Flattening changes only the fields and notes.

Can a flattened PDF be unflattened?

No. The fields and comments are gone as objects. That is why you flatten a copy.

Does flattening protect a PDF from editing?

It removes the easy way to change answers. It is not a lock: someone with a PDF editor can still alter page content.

What does flattening a PDF mean?

A PDF has layers of a sort: the page itself, and on top of it things that can still be changed, such as form fields, comments and highlights. Flattening presses that top layer into the page.

Updated November 12, 2026

What flattening changes

Before: a filled-in form field is a box with a value. Anyone can click it and type something else. A comment is a note attached to the page that can be edited, hidden or deleted, and may not print at all.

After: the value is drawn on the page like any printed text, and the box is gone. Comments and highlights become part of the page picture. What you see is what every reader, printer and app will show, and none of it can be edited as a field or a note.

When to flatten

Flatten a copy when the document is finished and should stay as it is:

You filled in a form and are sending it back, and the answers shouldn’t be changed by accident or on purpose.
The recipient’s app or printer shows empty fields or drops your comments. Flattened, they are simply page content.
You are archiving a reviewed document with its highlights and notes as part of the record.
A portal rejects PDFs with form fields or annotations.

When not to

Don’t flatten your only copy of a form you may need to correct: the fields are gone for good. Keep the original and flatten a copy.

Don’t flatten a digitally signed PDF: any change stops the signature from verifying. And don’t use flattening to hide information. A flattened highlight over a name still has the name underneath as text; removing it takes redaction.

What flattening does not change

The page text stays real text: it can still be selected, searched and read by a screen reader. Links keep working and bookmarks stay. The file doesn’t become a picture, and it doesn’t get much smaller or larger.

On this site, Flatten does the work in your browser, without uploading the file. A comment that has no drawn appearance of its own can’t be pressed into the page; it is left as it was, and the result tells you how many were.

Tools for this

Flatten Lock in filled forms and comments

Files are processed on this device and never uploaded.

Questions

Is flattening the same as “Print to PDF”?: The result is similar for form fields and comments, but printing to PDF also rebuilds the whole file: links and bookmarks are lost, and text may be affected. Flattening changes only the fields and notes.
Can a flattened PDF be unflattened?: No. The fields and comments are gone as objects. That is why you flatten a copy.
Does flattening protect a PDF from editing?: It removes the easy way to change answers. It is not a lock: someone with a PDF editor can still alter page content.