為 PDF 加上密碼
加密您的 PDF，只有輸入您設定的密碼才能開啟。
運作方式
1. 上傳您的 PDF。2. 輸入密碼並再次確認。3. 下載——檔案會經過加密（AES-256），只有輸入該密碼才能開啟。
我的密碼會被傳送到任何地方嗎？
不會——加密完全在您的瀏覽器中進行。您的檔案與密碼絕不會離開您的裝置。
如果我忘記密碼怎麼辦？
無法救回——這是真正的加密，一旦忘記密碼，任何人（包括我們）都無法開啟這個檔案。請將密碼妥善保存。
這使用什麼加密方式？
AES-256，也就是目前 PDF 標準的加密強度，透過廣泛使用的開放原始碼 qpdf 引擎，在您的瀏覽器中執行。
Does this work on a mobile browser?
Yes — it's a regular web page, not an app, so it works the same way in a mobile browser as on desktop. Tap to pick the file, set a password, and download the encrypted result — the encryption still happens entirely on your device.
Does this restrict printing or copying, not just require a password to open?
No — it's a single password that's required to open the file. Once someone has entered it, they can print, copy, and edit like normal; there's no separate owner password or permission controls that limit what an already-authenticated reader can do. Worth knowing anyway: those "disable printing/copying" options other tools offer are only honored by well-behaved PDF readers — anyone can strip them by printing the file to a new PDF.
What makes a good password for this?
Something reasonably long that isn't a guessable word — not your birthday, not "password123". We only require 4 characters minimum so we don't block anyone, but since there's no permission system backing this up, that password is the only thing standing between someone and the file. Treat it like a real password.