Flatten PDF

Flattening merges interactive elements -- form fields, dropdowns, checkboxes, annotations, highlights, sticky notes -- directly into the page content. The visual appearance stays the same, but nothing is editable or extractable anymore. It is the PDF equivalent of printing a filled-out form and scanning it back in, except the quality stays perfect.

How It Works

1. Upload one or more PDF files.
2. Click Flatten PDF.
3. A single file downloads directly. Multiple files produce a ZIP archive.

The tool uses pdf-lib to flatten form fields (via form.flatten()) and a dedicated annotation flattener to burn annotations into the page stream. Both operations happen in a single pass.

What Gets Flattened

• Form fields: Text inputs, checkboxes, radio buttons, dropdowns, signature fields
• Annotations: Comments, highlights, strikethrough, underline, sticky notes, stamps, ink annotations
• Interactive elements: Buttons, action triggers

What Stays Unchanged

• Text content (remains selectable and searchable)
• Images and graphics
• Page layout and dimensions
• Bookmarks and table of contents
• Hyperlinks (unless they are annotation-based)

Use Cases

• Locking a completed form so recipients cannot change the submitted answers
• Preparing a PDF for archival where interactive elements are unnecessary
• Fixing display issues caused by annotations rendering differently across viewers
• Ensuring a signed document cannot be modified after the signature is applied
• Reducing file size by eliminating form field definitions and annotation objects

Tips

• Flatten after all edits are complete. There is no way to unflatten a PDF.
• If you need to flatten and also strip metadata, JavaScript, and attachments, use the Sanitize PDF tool instead -- it includes flattening as one of its options.
• Some PDFs report "no form found" -- this is normal if the document only has annotations and no form fields.

Related Tools

• Sanitize PDF -- flatten forms plus remove metadata, scripts, and more
• Rasterize PDF -- convert to image-based PDF for maximum flattening
• Font to Outline -- flatten fonts to vector paths
• Encrypt PDF -- lock the flattened PDF with a password