What Does Flattening a PDF Mean and When to Do It

Flattening a PDF merges everything into the page itself — annotations, form fields, layers — so the file looks identical everywhere and can't be edited as easily.

What flattening actually does

• Annotations (comments, highlights, drawings) become part of the page content.
• Form fields become fixed text/images — no more editing.
• Layers are merged into a single visible result.
• Fonts and rendering are locked — every viewer shows the same output.

How this tool flattens

Flatten PDF renders every page to a single image and rebuilds the document. The result is a true flattened file with a consistent appearance everywhere.

When to flatten

The trade-off you must know

Flattening via rasterization means text becomes part of the image — no longer selectable or searchable. For searchable output, flatten only when you truly need the lock-in.

Related operations

• Redact PDF — cover sensitive content (pair with flatten to make it permanent).
• Sanitize PDF — remove scripts and hidden data.
• Create PDF/A — archival conversion, also rasterization-based in its most compatible mode.

Frequently asked questions

Does flattening reduce file size?

Usually increases it slightly because pages become compressed images.

Can I unflatten a PDF?

No — that's the point. Keep the original if you may need to edit later.

Is flattening private?

Yes — rendering happens locally in your browser.

Flatten your document now with Flatten PDF.