How your files are handled

When you fill, sign, redact, edit, or convert a PDF with AttachKit, the document is parsed and changed entirely in your browser— using JavaScript (pdf-lib, pdf.js) and WebAssembly (for on-device OCR when you scan an image-only PDF). We don't upload, store, or transmit the PDF itself. You can confirm this yourself: open your browser's Network tab while you edit — the file bytes never go out. (Two flows are exceptions, because their whole job is to get the document to someone else: Send for signature and the QR phone handoff. Both are covered below.)

Outside those two, the work happens locally and your document never touches our servers — there is nothing for us to retain, because we never had it. This is the core of how AttachKit is built. Where we do hold something, we say so below rather than rounding it off.

What does leave your browser?

• AI features (optional): when you use AI auto-fill or AI redaction suggestions, only the relevant text — never the file — is sent to the AI provider to generate the result.
• Account & email: if you sign in or send to others for signature, your email and the recipients' emails are handled to deliver those messages.
• Send for signature: one of the two flows where document bytes do leave your browser — we hold a copy encrypted in your browser (ciphertext, stored without any key that would open it) so your recipients can open and sign it. We delete it 7 days after you create the request; signing it doesn't delete it sooner, and closing your account takes your name and email off the request rather than removing the encrypted document, which still goes at that 7-day mark. By default the key rides in the link, and since we email that link for you it passes through us and our email provider on the way to your recipient's inbox — so treat the link like a password. See Security for the architecture.
• Signing on your phone (the QR handoff): the other one. To get the document onto your phone we upload it, encrypted in your browser, on the same 7-day storage as above. The key goes to your phone in the QR code rather than over the network, but it is sent to us along with the upload — we neither save it nor email it on this path.
• Support: anything you type into a help ticket or contact form. Don't paste sensitive document contents there.

Read the details

For the full, legally-binding specifics, see our Privacy Policy and Security pages.