How to Password Protect a PDF and Lock Printing, Copying or Editing on Your Device
Learn how to encrypt a PDF with a 128-bit password, choose which permissions readers keep, and download the protected copy without uploading the file.
PDF Password Add
Introduction
Contracts, invoices and reports often need a password before they are emailed or shared through a link. PDF Password Add loads the document with pdf-lib, encrypts its content streams with 128-bit RC4 using the standard security handler and writes an encryption dictionary that carries your chosen permission flags. The whole process, including key derivation, runs in the browser and the file is never uploaded.
Step-by-Step Instructions
- Drop a PDF onto Select or Drop PDF File to Encrypt & Protect or click Choose PDF Document; the card shows the file size and page count.
- Type the password in the Password field and watch the Strength meter, which rates length, uppercase letters, digits and symbols.
- Re-enter the same value in Confirm Password; a mismatch warning appears until both fields agree.
- Tick or untick Allow Printing, Allow Copying Text & Graphics and Allow Editing & Form Filling under Security Permissions.
- Click Protect & Download PDF to save a copy named with the _protected suffix.
Key Use Cases
- Client Deliverables: Send a proposal that opens only with a password shared over a separate channel.
- Read-Only Handouts: Block copying and editing on course material while leaving printing enabled.
- Internal Drafts: Lock editing on a draft so reviewers can read it but not change the pages.
Frequently Asked Questions
What encryption does the tool apply?
It writes a Standard security handler dictionary with V 2, R 3 and a 128-bit key, which is the RC4 128-bit scheme defined in the PDF specification. The key is derived from the password with MD5 padding, and the same password is used for both the user and owner passwords. Readers must enter it to open the file.
How do the permission checkboxes work?
Each box clears or sets a bit in the P value of the encryption dictionary: print, modify and copy. By default printing and copying are allowed and editing is off. Viewers honour these flags when the document is opened with the user password, but because the owner password is the same as the user password, anyone who knows it can lift the restrictions.
Can I use a weak or short password?
Yes. The strength meter is advisory only and does not block the download; it scores a point each for 6 or more characters, 10 or more characters, an uppercase letter, a digit and a symbol, labelling the result Weak, Good or Strong. The only hard requirements are a non-empty password and a matching confirmation.