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OPTIMIZE
Turn form fields, comments and annotations into a fixed part of the page, so nothing can be changed or lost.
QUICK ANSWER
To flatten a PDF, add the file and choose Flatten this PDF. Form fields, their answers and annotations are drawn into the page, so they print correctly and can’t be edited. It runs in your browser, so your file isn’t uploaded.
Updated 31 October 2026 · Written by the StackPDF teamUpdated 31 October 2026 · StackPDF team
Form fields and comments will be fixed in place. It stays in this browser.Form fields and comments will be fixed in place. It stays in this browser.
PDF files · Runs in your browser
QUICK ANSWER
To flatten a PDF, add the file and choose Flatten this PDF. Form fields, their answers and annotations are drawn into the page, so they print correctly and can’t be edited. It runs in your browser, so your file isn’t uploaded.
Updated 31 October 2026 · Written by the StackPDF teamUpdated 31 October 2026 · StackPDF team
HOW TO
Drop a filled-in form or a PDF with comments, from your computer, your phone or My files.
StackPDF counts the form fields and comments it finds.
Everything looks the same, but nothing can be edited any more.
GOOD TO KNOW
The page looks the same. What changes is whether anything can still be edited.
| ITEM | BEFORE | AFTER FLATTENING |
|---|---|---|
| Form fields | Can be typed in or changed | The answers become part of the page |
| Comments and highlights | Can be moved, edited or deleted | Fixed in place, printed as they look |
| Drawn signatures | An annotation that can be removed | Part of the page |
| Page text | Selectable | Still selectable |
Flattening can’t be undone, so keep the original if you might edit it again.
PRIVACY
Yes. Flatten PDF runs in your browser, so the file never leaves your device.
StackPDF opens the PDF in your browser tab and does the work there.
Close the tab and it’s gone. Free results download to your device. Premium can also keep them in My files.
pdf-lib, PDF.js and qpdf do the work, inside your browser.
FAQ
It turns form fields, comments and other annotations into a normal part of the page. The PDF looks the same but can no longer be edited.
Yes. The free plan includes 1 PDF export a day, with no account. Premium removes the daily limit for $5.99 a month or $39.99 a year.
No. Flattening happens in your browser, so the PDF stays on your device.
So the answers print the way you see them and nobody can change them afterwards. It also stops fields looking different in other viewers.
No. Flattening can’t be undone, so keep the original if you might edit it again.
Not usually, because it fixes things in place rather than removing them. Use Compress PDF to make the file smaller.