A strong PDF password is long, unique and impossible to guess from what people know about you. The easiest way to make one is to join four or more unrelated words into a passphrase, add a number or symbol if you like, and never reuse it from another account. Once you have it, you can lock the file in a minute with Protect PDF.
The password is the whole lock. A PDF with a weak one is like a door with the key left under the mat. This guide gives you practical ways to create a password you can remember and the recipient can type.
What makes a PDF password weak
Someone trying to open a locked PDF starts with the obvious guesses. These are the choices to avoid.
- Personal facts. Date of birth, phone number, ID number, house number, car plate. Anyone who knows you, or has another of your documents, can try them.
- Names. Yours, your child’s, your company’s, your city’s, with or without a year at the end.
- Common patterns. 123456, password, qwerty, abc123 and keyboard rows.
- The file’s own content. An invoice number as the password for that invoice, or the client’s name.
- Short passwords. A handful of characters can be guessed quickly by a program that simply tries every combination.
- Reused passwords. If your PDF password is also your email password, sharing the file means sharing the key to your inbox.
How to create a strong PDF password you can remember
Length does more for you than strange symbols. A long phrase of ordinary words is harder to guess than a short jumble, and far easier to say over the phone.
Method 1: the passphrase
Pick four or five words that have nothing to do with each other or with you. Look around the room, open a book at random, think of unrelated objects. Join them with a separator.
For example, a phrase in the style of lantern-biscuit-Tuesday-canal is long, easy to read aloud and not something anyone would guess. Do not use this exact example, since it is now published.
Method 2: the sentence shortcut
Think of a private sentence and take the first letter of each word, keeping the numbers and punctuation. “My first bike cost 900 rupees and I rode it to school!” becomes a string of letters, digits and a symbol that only you can rebuild. Use at least twelve characters.
Method 3: a password manager
If you already use a password manager, let it generate a long random password and store it. This is the strongest option, but check that the recipient can copy and paste it, because long random strings are painful to type on a phone.
Weak vs strong at a glance
| Type of password | Example style | Verdict |
|---|---|---|
| Date of birth | Eight digits | Weak. Easy to find and quick to guess. |
| Name plus year | Ahmed followed by a year | Weak. A very common pattern. |
| One dictionary word with a symbol | Sunshine! | Weak. Too short and too predictable. |
| Sentence shortcut, twelve or more characters | Letters, digits and punctuation from a private sentence | Good. |
| Four or more unrelated words | Words joined with dashes | Strong and easy to share by voice. |
| Long random string from a manager | Mixed characters | Strongest, but harder to type. |
How to add the password to your PDF
- Finish the document first. Do any merging, compressing or redacting before you lock it.
- Open the Protect PDF tool in your browser and add the file.
- Type your open password. Type it carefully, since one wrong character will lock you out too.
- Choose whether printing, copying and editing are allowed for people who open the file.
- Download the protected copy to your device.
- Open the download and enter the password to confirm it works before you send it.
PDFNova processes files in your browser, so your documents are not uploaded to a server. Neither the file nor the password you type is sent anywhere. If you want to understand why that matters, see the difference between browser-based and upload-based PDF tools.
Sharing and storing the password
A strong password shared badly is still a weak lock. Follow these rules.
- Use a second channel. Email the file, then give the password by phone call, text or chat app. Never write it in the same email.
- Do not put hints in the file name. A file called contract-pass-is-my-surname.pdf helps nobody but a snoop.
- Use a different password for each client or purpose. If one leaks, the others stay safe. Freelancers who send invoices and contracts regularly will find more routines in our PDF tips for freelancers.
- Record it somewhere safe. A password manager or a notebook kept at home works. There is no “forgot password” button on a PDF.
- Keep the unlocked original. Store your own unprotected copy securely on your device so a lost password is never a disaster.
What a password does not do
Be realistic about the limits. An open password stops people who do not have it from reading the file. It does not stop a recipient who has the password from sharing the document, and anyone with the password can save an unlocked copy.
It also does not hide anything inside the document from the person who opens it. If parts of the page should never be seen, remove them with Redact PDF before you lock the file. And if the person at the other end needs a paper copy, point them to how to print a password-protected PDF.
Frequently asked questions
How long should a PDF password be?
Longer is better. As a practical rule, aim for at least twelve characters, or four or more unrelated words. Length matters more than a single symbol stuck on the end of a short word.
What happens if I forget the password to my own PDF?
You will not be able to open that copy. PDF passwords cannot be reset, and the Unlock PDF tool only works when you enter the password you already know. This is why you should keep the original and record the password safely.
Is it safe to use my date of birth as a PDF password?
It is a poor choice for a password you pick yourself. Dates of birth appear on many documents and are among the first things someone would try. Some organisations send statements locked with a formula based on personal details, but when the choice is yours, use something that cannot be worked out.
Can I use the same password for every PDF I send?
It is better not to. Every person who ever received one file could then open all the others. Use a separate password for each recipient at least.
A few unrelated words are all it takes to turn a weak lock into a strong one. Choose your passphrase, open Protect PDF, and test the locked copy before it leaves your device.