How PDF flattening works
Flattening makes a PDF more consistent by converting interactive and layered elements into fixed page content. That helps ensure form values stay visible, layers don’t toggle unexpectedly, and the document renders similarly across browsers, email previews, and PDF readers.
When to use this tool
Flatten PDF is most useful when a document needs to be “final” — the layout should not shift, form values should stay visible, and the file should open reliably on other devices.
- Filled forms: lock in typed fields before sending to HR, banks, schools and government portals.
- Printing and signing: make sure checkboxes and form text actually show up on paper.
- Layered exports: simplify PDFs from design tools so viewers don’t hide or misrender layers.
If you want a smaller “final” file after flattening, use Compress PDF. If a PDF won’t open or fails during processing, try Repair PDF.
Step-by-step: flatten your PDF
Flattening follows the same short routine every time:
- Add your PDF files. Drag and drop PDFs onto the box above, or click it to select files from your device.
- Choose a flatten level. Balanced is a dependable everyday option for most forms and layered PDFs.
- Adjust quality and downscale (optional). Higher values preserve more detail, while downscaling can reduce output size.
- Flatten the PDFs. Click Flatten PDF. Everything runs locally in your browser.
- Save the simplified files. Download each flattened PDF or use Save all PDFs to save everything.
Privacy, limits and how this tool treats your files
FileYoga is built around a simple rule: your files stay with you. This tool follows that rule closely.
Local-only processing
Your PDFs are processed in your browser. We do not upload, scan or store your files on FileYoga servers.
No hidden copies
When you clear the list or close the tab, the tool stops using your files and does not save copies on a server.
No artificial limits
No paywalls or quotas. The only limits come from your device’s memory and your browser.
No account required
Use the tool without signing up. Open the page, flatten your PDFs, and leave when you are done.
Practical limits: very large PDFs can exceed browser memory, and password-protected or permission-restricted PDFs may fail unless you provide an unlocked copy.
Flatten levels: light, balanced and strong
Flattening is a trade-off between editability and consistency. The level slider gives you a quick way to choose how “final” the output should be.
Minimal flattening aimed at improving viewer compatibility while keeping the document closer to the original. Useful when you want fewer rendering surprises but still want flexibility.
A dependable everyday setting for forms and layered PDFs. It aims to lock in the visible result so form values and layered content show reliably across viewers.
The most “final” option. Best for printing, submissions and handoffs where you want to reduce the chance of edits or viewer-specific differences.
Quality and downscaling: when to use them
Use output quality and downscale to manage the trade-off between detail and output size, especially for image-heavy pages.
- Output quality: higher values keep fine text and line detail sharper; lower values reduce size more.
- Downscale pages: reduces resolution. Try 90–95% for a gentle reduction, or 85–90% for big scans.
Tips for best results
- Flatten after filling a form to keep typed values and checkmarks visible in other viewers.
- For printing, use Balanced and keep downscale at 100% if you want maximum clarity.
- If the output looks soft, increase quality or keep downscale closer to 100%.
- If a file is huge, flatten one PDF at a time to reduce memory pressure.
- Password-protected or restricted PDFs may fail unless you provide an unlocked copy.
Troubleshooting
- My filled fields still don’t show in some viewers: Try Strong to make the output more “final,” then re-check in the target viewer.
- The output is not editable anymore: That’s expected for flattening. Keep your original PDF as the editable version.
- The file fails or freezes: The PDF may be large or complex. Try one file at a time, close other heavy tabs, or slightly downscale pages.
- “Encrypted” / permission errors: Use an unlocked copy. Restricted PDFs often can’t be processed in-browser.
- Output is bigger than expected: Lower Output quality slightly or downscale to 95–90% (especially for image-heavy pages).
Frequently asked questions
No. Flattening happens locally in your browser. Your PDFs are not uploaded to FileYoga servers, and we don’t store copies of your documents.
Flattening turns interactive or layered parts of a PDF (like form fields, annotations, and optional layers) into fixed page content so the document looks the same across viewers — and filled form values stay visible.
Filled values are the main reason to flatten. In most cases the visible text/checkbox marks are locked into the page, which can make fields non-editable afterward. If you need to keep the form fillable, keep the original PDF too.
Light aims for minimal change, Balanced is the everyday choice for forms and layered PDFs, and Strong prioritizes “looks the same everywhere.” In Strong mode, the tool may use a fallback that renders pages to images when a PDF is complex, heavily layered, or unreliable in other viewers.
If the output stays PDF-native (text/vectors preserved), the size may change only slightly. If the tool uses the Strong fallback and rasterizes pages into images, size depends heavily on quality and downscale. Lower quality a bit or downscale to 95–90% to reduce size.
Often, yes. Flattening is designed to reduce viewer-specific behavior like layers toggling off, transparency oddities, or form appearances not showing. If a file renders differently across apps, try Balanced, and use Strong for the most consistent appearance.
Flattening is about making the PDF more final. Some interactive elements may be converted into fixed content. If the tool falls back to image-based output in Strong mode, text may no longer be selectable and some clickable elements may not behave the same. Review the result if links or selection matter.
If a PDF is encrypted or permission-restricted, browsers often block processing. Export an unlocked copy from the original app (or remove restrictions if you have permission), then flatten that version here.
There are no artificial limits. The practical limit is your device memory and browser performance. If a PDF is huge or image-heavy, flatten fewer files at a time, lower quality slightly, or downscale pages.