Software & Apps Windows What Is a Document Open Password? How to protect your PDF docs By Tim Fisher General Manager, VP, Lifewire.com Tim Fisher has 30+ years' professional technology support experience. He writes troubleshooting content and is the General Manager of Lifewire. our editorial process Facebook Twitter LinkedIn Tim Fisher Updated November 12, 2019 Windows The Ultimate Laptop Buying Guide Tweet Share Email A document open password is a password used to restrict the opening of a PDF file. In contrast, PDF owner passwords are used to provide document restrictions in PDF files. While this password is called the document open password in Adobe Acrobat, other PDF programs may refer to this password as the PDF user password or the PDF document open password. How to Set a Document Open Password on a PDF Some PDF readers may let you protect the opening of the PDF with a password but it's usually specialized tools that include that option. There are also some PDF creators that have the option of creating a PDF user password. With tools that create PDFs, you normally have to start off with a file that isn't a PDF (since the idea is to create a PDF), and therefore aren't all that helpful if you're wanting to make a document open password for an existing .PDF file. You can install the free trial of Adobe Acrobat to protect a PDF with a password, or of course, use the full version if you have it. Use the File > Properties... menu and then the Security tab to find the Security Method option. Choose Password Security and then select the option in the new window called Require a password to open the document. Enter a password in that text field to create the document open password for the PDF file. Two other options for adding a password to a PDF is to use the Soda PDF or Sejda website. They're very easy to use: upload the PDF file to the website and then enter the password you want to use. The Password Protect PDF page on Smallpdf.com is a similar website where you can stop a PDF from opening unless the password of your choosing is entered. Smallpdf.com limits the number of PDF files you can use on its website to two per hour. How to Crack or Remove a PDFs Document Open Password Document open passwords are not easily hacked but there are a few PDF password recovery tools that can do it via a brute-force attack, given enough time. The website Smallpdf.com is one example. After attempting to remove the password for you, it will ask you to enter the password yourself if it doesn't succeed. Either way, it removes the password for you so that you can then download it back to your computer and use it as a regular PDF file. Like I said above, Smallpdf.com can only deal with two PDFs per day, for free users. This means you can set a password on two PDFs, remove the user password on two PDFs, or do a combination of both, but only involving two files within each hour. To simply remove the password, you can open the PDF in Adobe Acrobat. It will, of course, make you enter the password before you can move forward, after which you can follow the same steps as described above for setting the user password, but by choosing No Security instead of Password Security. While the Soda PDF website I mentioned above is used for securing a PDF, the Soda PDF Unlock PDF page lets you remove the password. Unlike a PDF password cracker, you have to know the password. This website is useful if you're just wanting to remove the password protection.