Flatten PDF
Local Processing (Offline Capable)Merge form fields into read-only page content for tamper-proof distribution; outputs an optimized copy when no forms are present. Unlike Sanitize, flattening targets form fields only without deleting scripts or metadata.
How this tool works (no sign-up needed)
- Upload your file above. Each tool shows whether it runs Local (in your browser) or Cloud (encrypted servers).
- Adjust options, then click the Run / Convert / Process button.
- Wait for progress, then download the result. Use Next tools to continue.
If buttons are not visible, enable JavaScript — the interactive workspace loads in your browser.
Free · LocalMerge form fields into page content — read-only output
Supports application/pdf
Local — your file is processed in your browser and not uploaded to us. No account needed.
What is it?Flatten PDF is a PDFLean optimization tool: Merge form fields into read-only page content for tamper-proof distribution.
TL;DR: Merge form fields into read-only page content for tamper-proof distribution. Everything runs locally in your browser — your file is never uploaded, and closing the page clears it immediately; flattened forms cannot be edited again.
Measured: ~21 ms median on a typical sample — full benchmark table below.
This tool processes PDF documents that contain form fields, merging those interactive fields into read-only page content for tamper-proof sharing. Processing runs entirely in your browser's memory — the document is never transmitted, and closing the tab clears it completely. The output is a flattened PDF in which form data is baked into the page content; when the input has no form fields, an optimized copy is returned instead. Key limitation: forms can no longer be edited after flattening, and files larger than 10 MB are not supported since processing happens inline in the browser.
About this tool
No accounts, no uploads, no watermarks — just the operation you came for. Merge form fields into read-only page content for tamper-proof sharing. Unlike Sanitize, this targets form fields only. Processing runs locally in your browser's memory — the document is never transmitted, and closing the tab clears it completely. The workflow is deliberately short: load the file, choose the options on the page, run the operation, and save the result. Every choice is applied before the file is written, so re-running with different settings takes seconds. Practical limits apply (see the on-page limits); it pairs well with the related tools linked beside this page when one step is not the whole job. Key facts — Processing: runs entirely in your browser, client-side; Access: free with no account required; File limits: see the on-page limits; Privacy: the file never leaves the device.
Measured performance benchmarks
| Sample | Input | Output | Median time | Size change |
|---|---|---|---|---|
| Flatten form fields (60-page report) | 160 KB | 158 KB | 21 ms | −1% |
Measured locally in your browser (isomorphic production code; samples are programmatically generated text PDFs, median of 5 runs). Real-world image-heavy PDFs differ — see the on-page limits.
How to use
Upload a PDF with form fields
Click "Flatten PDF"
Download the read-only output
FAQ
Will my file be uploaded?
No. Everything runs locally in your browser — your file is never uploaded, and closing the page clears it immediately.
Are there any limits?
Flattened forms cannot be edited again; single file size limit is ≤ 10MB (browser inline processing).
Will flattening affect digital signatures or XFA forms?
Flattening removes form field interactivity and invalidates existing digital signatures in signed documents. In addition, only AcroForm fields are merged into page content — XFA forms are not flattened.
Can I process multiple files in bulk?
A single tool page handles one task at a time; for bulk work use the Batch Processing workflow and add this tool as a step to run a whole set at once.
Is the processed file still editable?
The output is still a standard PDF that opens in any PDF reader; the original document is untouched and you receive a new file; however, flattened form content becomes read-only page elements and can no longer be filled as form fields.