Flatten PDF
Merge filled-in form fields, comments, stamps and other annotations into the page content so nobody can change them, or turn every page into a flat image. Your PDF is processed in the browser and never uploaded.
Show fields and annotations
| Page | Kind | Name / type | Value / content |
|---|
How to use the Flatten PDF
- Open a PDF with the Open PDF button or drop it onto the drop area. The tool counts pages, form fields and annotations.
- Choose a mode: Flatten forms & annotations keeps text selectable; Flatten everything to images locks everything into pictures.
- Adjust the options, such as keeping links clickable or the image resolution.
- Press Flatten PDF and wait a moment.
- Download the flattened PDF and check it in your PDF reader.
What gets flattened
| Element | Flatten forms & annotations | Flatten everything to images |
|---|---|---|
| Text fields, checkboxes, radio buttons, dropdowns | Merged into the page as vector graphics; field removed | Captured in the page image |
| Comments, highlights, stamps, drawings, shapes | Merged using their appearance stream | Captured in the page image |
| Text boxes without an appearance | Redrawn as plain text with a border | Captured as pdf.js displays them |
| Hyperlinks | Kept clickable (optional) | Removed |
| Page text | Still selectable and searchable | Becomes part of the image (not selectable) |
| File size | About the same as the original | Usually larger; depends on DPI |
How form flattening works
Every form field and annotation in a PDF comes with an appearance stream: a small drawing that tells viewers what the field or comment looks like. Flattening copies that drawing into the page's own content, scaled to the annotation's rectangle, and then deletes the interactive object. Field values that were changed without updating their appearance are redrawn first with Helvetica so the flattened page shows the current value. After flattening, the form (AcroForm) is removed, so PDF readers no longer show fillable boxes.
The image mode is a different approach: each page is rendered with pdf.js exactly as you would see it on screen, including all forms and annotations, and the pictures are assembled into a new PDF with pdf-lib at the original page size. Nothing in that file can be edited, selected or extracted as text without OCR.
Tips
- Fill and sign first. Use Fill PDF Form or Sign PDF, download the result, then flatten it here.
- Keep the original. Flattening cannot be undone, so save the fillable version too.
- Check before sending. Open the flattened file and try clicking a field; it should no longer be editable.
- Too big? Image-mode files at 300 DPI can be large. Use 150 DPI, or shrink the result with Compress PDF.
Frequently asked questions
What does flattening a PDF mean?
Flattening merges interactive layers into the ordinary page content. Filled form fields become plain text and graphics, and annotations such as comments, highlights, stamps and drawings become part of the page, so they look the same everywhere but can no longer be edited, moved or deleted.
Why should I flatten a filled PDF form?
A flattened form cannot be changed by the next person, displays the same in every viewer (some apps and phones hide form values or show them in different fonts), and prints reliably. Many agencies, courts and e-signing workflows ask for flattened forms.
Which mode should I choose?
Use Flatten forms & annotations for most documents: the result stays small and the page text remains selectable and searchable. Use Flatten everything to images when you need a copy that is practically impossible to edit, or when a field or annotation does not flatten correctly in the first mode.
Can a flattened PDF be unflattened?
No. Flattening removes the form fields and annotation objects, so the original values cannot be edited as fields again. Keep a copy of the original fillable PDF if you might need to change it later.
Why did an annotation stay editable?
Annotations are baked into the page using their appearance stream, the drawing that viewers display. A few PDFs contain annotations without one (for example some sticky notes). Text box annotations without an appearance are re-drawn as plain text; other types are left as they are and counted in the result. The image mode always captures what pdf.js displays.
Is it safe to flatten confidential documents here?
Yes. Everything runs in your browser using pdf-lib and pdf.js. The file is never uploaded to a server, and nothing is stored after you close the page.