Flatten PDF — Lock Form Fields & Annotations

Flatten PDF is built for PDF document workflow jobs that fit cleanly into a browser tab. Flatten form fields, annotations, and layers in a PDF to make content non-editable and static. The processing runs in the page itself, which is why the controls update instantly when you change settings and why a freshly loaded page is ready to do real work the moment it becomes interactive.

Reach for Flatten PDF when you need a predictable result on a single file. The page works on the first visit, the controls are visible without a menu, and the output is delivered the moment the engine finishes.

The execution path is auditable from the page itself: open developer tools, switch to the Network tab, run a job. The requests you see are static-asset GETs for the engine and the page resources. The actual work is JavaScript code running against the bytes already in your tab's memory.

Flatten PDF is implemented on top of the open-source pdf-lib JavaScript library. The accepted input formats are PDF, decoded in the browser, processed, and re-encoded into the output format. Files up to 200 MB are well within the comfort zone of any modern browser.

On limits: 200 MB per file is the ceiling. Output formats and quality settings are listed in the controls panel above, and they apply to every run.

If you fit any of these descriptions, Flatten PDF should slot cleanly into your workflow: students assembling reading packets; researchers archiving reference papers; freelancers sharing scanned receipts. The tool keeps the controls focused on what matters for each of these use cases.

The download is delivered as `{name}-flattened.pdf` the moment processing completes — no email link, no "your result will be ready in 5 minutes" queue, no expiry timer. The file is generated in your browser and saved by your browser's normal download flow.

Flatten PDF is intentionally narrow in what it does, which makes it easy to slot into a longer workflow. Take its output, hand it to whichever next tool fits the job, and Flatten PDF stays out of your way until the next time you need it.

Flatten PDF keeps the control set focused. Every option on the page is there because a real workflow needs it, and the defaults aim at the most common case so a first-time user can get the right output without changing any settings.

A short note on how Flatten PDF came to look the way it does: every iteration started by watching how someone unfamiliar with the tool actually used it, then removing whatever got in their way. That is why the upload area dominates the screen, the run button is bigger than the secondary controls, and the result panel is unmissable when the job finishes.

Flatten PDF produces deterministic output: the same input plus the same options always produces the same result. That predictability matters when the result has to match an upstream specification or be reproducible later.

Pro tip: Flatten PDF works just as well in a private/incognito window as in a normal one, which is occasionally useful when you want zero browser-history footprint of the job. Another tip: if the tool ever feels slow, it is almost always because the browser tab is competing for CPU with another tab — pausing or closing the heavy ones gives the engine room to work.

If Flatten PDF appears to hang, the engine is almost certainly still working — large inputs simply take longer to process inside a browser than they would on a server with multi-core scheduling. For inputs near the 200 MB cap, give it up to a minute on a typical laptop before assuming something is stuck.

Flatten PDF is one of many single-purpose tools in the catalog. Each is built around the same single-page model. Use this one, close the tab, and come back the next time you need the same job done. None of the tools require prior knowledge of the others — each page is self-contained.