About this tool
Adding a password to a PDF locks the document so it can only be opened (or modified, depending on permissions) by someone who knows the password. PDF supports two passwords: user (required to open the file) and owner (required to change permissions like printing or copying).
This tool encrypts in-browser with AES-256, the modern PDF encryption standard. Your file never leaves your device. You can set both passwords or just one. Granular permissions let you allow viewing while blocking copy / print / edit.
How it works
Open your PDF
Drop the file you want to protect.
Set a user password
This password is required to open the PDF.
Optionally set an owner password
Required to change permissions (print, copy, edit). If you skip, anyone who can open the file can change permissions.
Pick permissions
Allow / disallow printing, copying text, modifying, filling forms.
Encrypt and download
The protected PDF saves to your device.
Use cases
Confidential contracts
Send a contract draft for review without risking it being freely re-shared.
HR documents
Salary letters, NDAs, performance reviews - block copy and print on the file.
Tax filings
Lock the file with a password before emailing it to an accountant.
Client deliverables
Watermark + password prevents the deliverable from being passed around without your involvement.
Format and spec details
| Encryption | AES-256 (PDF 1.7 standard) |
|---|---|
| Passwords | User (open) + Owner (change permissions) |
| Permission flags | Print, Copy text, Modify, Fill forms, Annotate |
| Removable? | Anyone with the password can remove via PDF Unlock |
Tips and best practices
- Use a strong user password: 12+ characters, mixed case, numbers, symbols.
- Owner password is for permissions - if you do not set one, anyone can change the file.
- Disable "Copy" if you do not want the text extracted - blocks both bulk copy and screen-scraping.
- Test the protected file in another viewer to confirm the password is required.
How to use the PDF Protect
The PDF Protect is a browser-based tool that runs entirely on your device. Inputs you enter never reach a server - all calculations happen client-side in JavaScript. This means:
- Privacy: nothing is logged, sent, or stored by 3Tej. Inputs disappear when you close the tab.
- Speed: results update as you type. No network round trip.
- Offline use: once the page is cached, it works without internet.
- No signup: no account, no email, no rate limits.
Step by step
- Enter your inputs in the form above. Each field is labeled with its unit (currency, percent, kg, etc.) and the expected range.
- Read the result as it updates. The number reflects the formula commonly accepted in PDF Protect-related calculations.
- Adjust to see sensitivity: change one input at a time and watch how the output moves. This is the fastest way to understand which variable matters most.
- Copy or screenshot the result for later reference. The page state persists for the session if your browser allows it.
When you would use this
- Quick estimates: when you need a number now and don't want to open a spreadsheet.
- Sensitivity analysis: testing how a result changes as inputs vary, before committing to a real-world decision.
- Comparison: running the same calculation with different inputs to compare options side by side.
- Learning: building intuition for how the underlying math behaves.
- Documentation: capturing a snapshot of inputs and outputs at a point in time.
Privacy and offline operation
Every operation in this tool runs client-side using your browser's built-in APIs (Canvas, Web Audio, WebAssembly). No data is uploaded. After the initial page load you can disconnect from the internet and the tool keeps working.
We use Google Analytics and AdSense for the page itself, but neither sees the content of the files you process.
Frequently asked questions
Is PDF password protection actually secure?
AES-256 protected PDFs are practically impossible to brute-force with a strong password (12+ characters, mixed case, symbols). Weak passwords (under 8 characters) can be brute-forced in hours.
What is the difference between user and owner password?
User: required to open the file. Owner: required to change permissions (e.g. allow printing). Setting both is most secure.
Can I disable copying or printing?
Yes - the owner password + permission flags disable copying, printing, modification.
Can I remove the password later?
Yes - use PDF Unlock with the password.
What if I forget the password?
There is no recovery if the password is strong. Always store passwords in a password manager.
Is the PDF Protect accurate?
The PDF Protect applies the standard formula for pdf protect. Accuracy is limited only by your input precision. For decisions with material consequences, use the result as a starting point and verify with a qualified professional or the relevant official source.
Is the PDF Protect free?
Yes. 100% free, no signup, no payment, no API key. The site is funded by display ads that appear around the tool but not inside the calculation flow.
Are my inputs saved?
No. Inputs stay in your browser tab. Closing the tab discards them. The site uses Google Analytics for traffic measurement (anonymized) but does not see what you type into the form.
Can I use the PDF Protect on my phone?
Yes. The tool is responsive and tested on iOS Safari, Android Chrome, and major desktop browsers. Touch targets meet Apple's 44pt and Google's 48dp minimum guidance.
How do I report a bug or suggest improvement to the PDF Protect?
Email hi@3tej.com with the URL of this page and a description of what you saw vs expected. We typically respond within 72 hours and update calculators when rules or formulas change.
How accurate is the PDF Protect?
It applies the standard formula. Accuracy is limited only by your input precision. For decisions with material consequences (taxes, medical, legal, structural), use the result as a starting point and verify with a qualified professional in the relevant field.
Is the PDF Protect free to use?
Yes. 100% free, no signup, no payment, no API key. The site is funded by display ads around the tool but not inside the calculation flow.
Are my inputs saved anywhere?
No. All inputs stay in your browser tab. Closing the tab discards them. The site uses Google Analytics for traffic measurement (anonymized) but the analytics never see what you type into the form.
Does the PDF Protect work offline?
Yes. Once the page has loaded, it works without internet. The calculation runs in JavaScript on your device.
Can I share results from the PDF Protect?
Take a screenshot or copy the output. The page doesn't generate shareable URLs for specific calculations - inputs stay in your browser only.
Why are the results different from another pdf protect tool?
Most likely: different formula assumptions, different default values, different rounding rules, or different applicable rates. Check the methodology if both tools document it. Both can be valid for different scenarios.