What are the two flatten modes?
**Keep forms as real text** locks fillable AcroForm field values into the page using pdf-lib. Text stays searchable and selectable. Comments, highlights, and stamps are not removed.
**Lock in everything on the page** renders each page with PDF.js, encodes it as JPEG, and rebuilds the PDF. All visible markup — comments, highlights, stamps — is baked in. Text becomes non-selectable, similar to printing to PDF.
Which mode should I use?
Use **Keep forms as real text** when you have fillable forms and want searchable, selectable text. Comments and highlights will remain editable.
Use **Lock in everything on the page** when you need comments, highlights, or stamps permanently embedded — for example before sharing a reviewed document or printing. Choose Balanced for most files or Smaller file if download size matters.
Is text still selectable after flattening?
It depends on the mode. **Keep forms as real text** preserves selectable, searchable text — only form interactivity is removed. **Lock in everything on the page** rasterizes each page, so text is no longer selectable — the output behaves like a scanned or printed PDF.
How is flattening different from Print to PDF?
**Keep forms as real text** is more precise than Print to PDF for forms — it locks field values without rasterizing the page. **Lock in everything on the page** is similar to Print to PDF: the page is rendered to an image, so text is not selectable but all visible markup is baked in.
What happens to comments and highlights?
In **Keep forms as real text** mode, comments and highlights are **not** removed — only form fields are flattened. In **Lock in everything on the page** mode, comments, highlights, and stamps are baked into the page image and will print and display consistently.
Are digital signatures preserved?
No. Flattening modifies the PDF structure and invalidates digital signatures. If you need signed documents, flatten a copy and keep the original signed file unchanged.
Does this tool support XFA forms?
No. XFA (XML Forms Architecture) forms are not supported. The tool works with standard AcroForm fillable fields. XFA-heavy PDFs may not flatten correctly — test with a copy first.
Is my PDF uploaded to a server?
No. Flattening runs entirely in your browser using pdf-lib and PDF.js. Your file is read from memory on your device and never sent to any server.
What are the file and page limits?
Maximum file size is 50 MB. In **Lock in everything on the page** mode, page count is capped at 40 on mobile devices and 80 on desktop to protect browser memory. **Keep forms as real text** mode does not have a separate page cap beyond the file size limit.
Can I undo flattening?
No. Flattening permanently locks content into the PDF. Always keep a backup of the original file before flattening.
Flatten PDF vs Compress PDF?
Flattening locks interactive content — fillable fields, comments, or highlights — so the PDF cannot be edited. Compressing only reduces file size and does not lock forms or bake in markup. Flatten first when you need a finalized document; compress afterward if the locked file is too large for email or uploads.