Flatten PDF: lock forms and annotations in your browser

Flattening merges interactive and layered content into the page itself. Form fields, comments, stamps and signatures stop being separate objects that can be edited and become fixed page content that looks the same everywhere.

No. Flattening runs entirely in your browser. PDF.js renders the pages and pdf-lib builds the new file on your device. Your document never leaves your computer or phone. Open the browser network tab while flattening to confirm no request carries your file.

Form fields only uses pdf-lib to turn fillable fields into fixed text. The text stays selectable and the file stays small. Flatten everything renders every page, including annotations, comments, signatures and form values, and rebuilds the PDF from images. It is the most thorough option, but text is no longer selectable.

With Form fields only, yes. With Flatten everything, no, because each page becomes an image. If you need searchable text afterwards, run the result through our OCR PDF tool.

Form fields only usually changes the size very little. Flatten everything can make the file larger or smaller depending on the content, because pages are stored as images. Choose Standard quality for smaller files and Print quality when sharpness matters.

Flatten everything does: comments, stamps, highlights and signatures are drawn into the page image. Form fields only flattens fillable form fields and leaves other annotations as they are.

It makes it much harder. Flattened content can no longer be changed as form fields or annotations. A page that is now an image cannot be edited as text, although someone could still redraw over it with an editor or run OCR. Flattening is not a security feature. To restrict opening, use our Protect PDF tool.

Not exactly. Flatten everything does rebuild each page from an image, so hidden text, layers and form data are not carried over. But it keeps everything that is visible on the page. To black out specific content, use the Redact tool in our PDF Editor first, then flatten.

Not yet. If the PDF needs a password to open, the tool cannot read it. Remove the password first with our Unlock PDF tool, then flatten the result.

Some PDFs only look like forms. They are flat pages with lines and boxes and no real fillable fields. There is nothing to flatten in that case, so use Flatten everything if you want to bake in other content, or the PDF Editor to add text over the form.

The limit is your device memory. Form fields only handles large files easily. Flatten everything renders every page, so documents with hundreds of pages take longer, especially on phones. Split the PDF first if it is very large.

Yes, in modern mobile browsers. Flattening a long document to images is slow on a phone, so a laptop is better for big files.