Are my PDFs uploaded anywhere?

No. Every tool runs in your browser using WebAssembly and JavaScript. Your files never leave your device.

How do I merge PDF files for free?

Open SubZero PDF Tools, choose Merge, drop two or more PDFs in the order you want, and download the combined file. It's free with no signup.

Can I compress a PDF without uploading it?

Yes. The Compress tool re-renders each page in your browser at a smaller size and quality. It works best on scanned or image-heavy PDFs.

Every PDF tool. In your browser.

Merge, split, compress and convert. Free, private — nothing leaves your device.

Drop PDFs here, or click to choose PDF files — add as many as you like

Pick a PDF tool

Everything runs on your device — your files never upload.

Organize

Merge PDF

Combine several PDFs into one file, in the order you add them.

Split PDF

Break a PDF into pieces by page ranges — each range becomes its own file.

Remove pages

Delete the pages you don't want and keep the rest.

Extract pages

Keep only the pages you choose in a brand-new PDF.

Rotate PDF

Turn every page — or just some — 90°, 180° or 270°.

Convert

Images to PDF

Turn JPG, PNG or WebP images into a single PDF, one image per page.

PDF to JPG

Render each page to a JPG image, delivered as a zip.

Compress PDF

Shrink the file size. Best for scanned or image-heavy PDFs.

Lossy

Edit

Page numbers

Stamp page numbers in the corner or center of every page.

Watermark

Lay diagonal text like “CONFIDENTIAL” across every page.

Server tools

PRO

Word / Excel to PDF

Convert Office documents to PDF. Needs a server — coming soon.

PRO

Protect / Unlock

Add or remove a password. Coming soon.

Good to know

Are my PDFs private?

Yes. Every tool here runs inside your browser with WebAssembly and JavaScript. Your files are never uploaded to a server.

Why is my compressed PDF barely smaller?

Compress re-renders each page as an image, which shrinks scanned or photo-heavy PDFs a lot but does little for PDFs that are mostly selectable text — those are already compact.

How do I choose page ranges?

Type page numbers or ranges separated by commas, like “1-3, 5, 8-10”. Pages are counted from 1.

Is there a file-size or page limit?

No hard limit, but because everything runs on your device, very large PDFs are bound by your device's memory. Big scans can take a moment.