Flatten PDF
Fill in a PDF form and lock the answers into the page
At a glance
- Use this page to flatten files quickly with a guided workflow.
- Accepted input: .pdf.
- Output: downloadable file generated in-browser for supported workflows.
- Upload Choose your file
- Process Runs locally
- Download Save result
Drop your file here
or tap to browse · accepts .pdf
Runs in your browser. No file uploads for supported tools.
Best on desktop for 100MB+ files · mobile recommended under ~100MB.
How local processing works
- Your PDF is processed in your browser using local JavaScript libraries.
- PDFWhisk does not upload your file to a processing server for supported tools.
- Only normal page assets load from the site (HTML/CSS/JS), not your document contents.
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Security & privacy detailsHow this tool helps
A fillable PDF keeps its answers in form fields that anyone can change, and some viewers, phones and print systems display those fields blank or with the wrong font. Flattening turns the answers into ordinary page content, so the form looks the same everywhere and the boxes can no longer be edited. That is what many HR departments, letting agents, solicitors and online portals mean when they ask for a flattened PDF or for a form that is not editable. Load your PDF and PDFWhisk lists its fields. You can fill in or correct text boxes, tick boxes, dropdowns and radio buttons right here, then flatten. Everything runs in your browser, so the personal details on the form are never uploaded. Use it when you need to fill in a PDF form on any device, sign the flattened form, password-protect it before emailing.
Best for
How it works
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1
Add a fillable PDF
PDFWhisk lists the form's text boxes, tick boxes and dropdowns.
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2
Check or fill the answers
Type or correct any answers on the page, or leave them as they are.
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3
Flatten and download
The answers are merged into the page so they can't be edited. Download the flattened PDF.
More files today? Free covers 3 tasks a day and files up to 50MB. For unlimited tasks and bigger files, Pro passes start at £1 for 24 hours. One-off payment, no subscription, and your files still stay on your device.
Flattening a PDF form: practical guide
Flattening is the last step before you send a completed form. Here is when it helps, the order to do things in, and what a browser tool can and can't flatten.
When you should flatten a form
Flatten when a recipient asks for a non-editable or flattened PDF, when answers show up blank in Mail on iPhone or in an online portal's preview, or when you want to be sure nobody can change your answers after you send them. It also stops print shops and older printers dropping the field contents.
The right order: fill, check, flatten, then sign
Fill in every field and check the answers, because flattening can't be undone. Flatten next. Add a drawn or typed signature with Sign PDF afterwards, and if the document needs a certified digital signature, apply that last of all, since any later change to a digitally signed PDF breaks the signature.
What is and isn't flattened
Text boxes, tick boxes, radio buttons, dropdowns and list boxes are merged into the page. Digital signature fields are left alone. Comments, sticky notes and highlights are annotations rather than form fields, so they stay as they are. Dynamic XFA forms (made with Adobe LiveCycle and found on some older official forms) only work properly in Adobe Reader; fill and flatten those in Reader instead.
Special characters and unusual fonts
When you change an answer here, the new text is drawn in a standard font. Accented letters common in Western European names work, but some letters (for example in Polish or Czech names), symbols and non-Latin scripts may not. If an answer doesn't look right in the flattened copy, fill that field in your PDF viewer first and flatten here without editing it.
Before you upload/share
- Open the flattened PDF and read every answer before you send it.
- Keep the fillable original in case an answer needs changing later.
- Password-protect the PDF if it contains personal details and is going by email.
Related guides
- How to Fill in a PDF Form Without Printing It
Most PDF forms can be filled in directly in a browser or PDF viewer without printing and scanning. Here is how to do it quickly and which tools actually work.
- How to Sign a PDF Without Printing It
Stop printing, signing, and scanning. You can add a signature to a PDF directly in your browser, free, private, and ready to send in under a minute.
Frequently asked questions
What does flattening a PDF mean?
It merges form fields into the page itself. The answers stay visible but become part of the page like printed text, so they can't be edited, cleared or lost when someone opens the file in a different app.
Can I fill in the form here before flattening?
Yes. After you add the PDF, its text boxes, tick boxes, dropdowns and radio buttons are listed. Change any answers, then click Flatten PDF. For long forms, filling in a dedicated PDF viewer first and flattening here also works.
Why does a website ask for a flattened PDF?
Fillable fields can display blank or garbled in some systems, and editable answers can be changed after submission. A flattened file shows exactly what you entered on every device and printer.
Can a flattened PDF be unflattened?
Not in practice. Once the fields are merged into the page, the original form fields are gone. Keep a copy of the fillable version if you might need to change answers later.
Does flattening work on scanned or non-fillable PDFs?
There is nothing to flatten in a PDF without form fields, and the tool will tell you so. Comments and annotations added in some viewers are not form fields; printing the file to PDF is the simplest way to fix those in place.
Are my form details uploaded?
No. The form is read, filled and flattened in your browser. That matters for application forms, tenancy paperwork and HR documents that contain personal information.
Does flattening remove a digital signature?
Signature fields are left as they are, but changing and re-saving a digitally signed PDF invalidates the signature. Flatten the form first, then have it signed.
What to do next
Chain tools together for a complete workflow.