There are different methods for creating a password for pdf,
If you have an Adobe-acrobat on your computer you can follow these steps;
How to password protect pdf with adobe
1- Click on View > Tools > Protection
2- Click on Protection > Encrypt > Encrypted with password.
3- Click on Ok to allow program change the security of this file.
4- If you want to create a password for opening the pdf, click on “require a password to open the document” box.
5- in document open password part, you can write your desired password.
6- If you want to restrict editing and printing of the document, you can tick “Restrict editing and printing of the document …”
7- In “Printing Allowed” tab, you can restrict printing the document and in “Changes Allowed” tab you can restrict changing the program.
8- in “Change permissions Password” tab you can describe permissions password.
9- In option part click on “Compatibility” tab here you can describe with which version adobe acrobat your pdf will be open, for instance, if you want to open your pdf in acrobat 9 you should choose “Acrobat 7.0 and later”
10- Click on ok.
11- Adobe acrobat ask you to confirm your open password.
12- Confirm your permission password.
13- These passwords will be applied to your pdf files when you save your file. it is better to “save as” your file and change the name of your new pdf because if you forgot your password you would not lose your file.
How to password protect pdf with Microsoft word
1- Open your pdf file with Microsoft word, if you have Microsoft word 2013 or later, you can easily open your pdf file with Microsoft word program.
2- Click on “File” tab and after that click on “Save as” key.
3- Choose your desired name.
4- Choose “Pdf” in save as type.
5- Click on the “Option” key.
6- Tick “Encrypt the document with password box”.
7- Enter your desired password.
8- Click on save key.
9- you should enter your password to open your file again.