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SlimFile

Add a password to a PDF

Lock a PDF with a password so only people who know it can open it. Up to 15 at a time, 25 MB each.

Choose your PDFs

up to 15 at a time.

PDFMax 25 MB each

How it works

  1. Step 1

    Drop a PDF

    Drag up to 15 PDFs onto the page, or browse for them. Each can be up to 25 MB.

  2. Step 2

    Choose a password

    Click the add-password button on a file and type a password, twice, to catch typos.

  3. Step 3

    Download it

    The file now needs that password to open, in any PDF reader — not just here.

How PDF password protection works

The password is required to open the file at all — in Adobe Acrobat, a browser, or anywhere else that opens PDFs. There's no way to recover a lost password, since it's never stored, so keep it somewhere safe.

Standard handler
the same PDF encryption Adobe Acrobat and most PDF software use
Never stored
the password is used once to protect the file and then forgotten
Replaces, not stacks
applying a new password swaps out the old protection

Why use SlimFile for this

  • Works in any PDF reader

    Uses the standard PDF security that Adobe Acrobat and every mainstream reader understand.

  • Your password is never kept

    It is used to lock the file and then discarded — which also means it cannot be recovered, so keep it safe.

  • Free, no sign-up

    No account, no email address, no trial that runs out.

  • No watermark

    What you download is clean — nothing added to your file.

  • Deleted within an hour

    Uploads and results are removed automatically about an hour after processing. We never look inside them.

Questions

How do I password protect a PDF before emailing it?
Add the PDF, choose a password and download the protected copy. Send the file by email and share the password another way, such as a message or a call.
What happens if I forget the password?
The file cannot be recovered — the password is never stored anywhere, so there is nothing to reset. Keep it somewhere safe.
Can I change the password afterward?
Open the add-password button again and enter a new one — it replaces the old protection rather than adding a second layer on top.
Is this the same protection as Remove PDF Password removes?
Yes — the standard PDF security handler used by Adobe Acrobat and most PDF software. Remove PDF Password can undo it again if you have the password.

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