You can easily apply for password protection on any PDF using the right software and tools. Try using DeftPDF online. It is free software that can add password protection to your PDF by just uploading your file to the tool, encoding your preferred password then clicking protect. Here is a step by step guide. Step one. Go to DeftPDF.com and click protect from all tools Step two. Upload your PDF file Step three. Encrypt your PDF by encoding your Password on the textbox. You can also add some limitations such as printing, copying, or commenting by clicking more options. Step four. Once done, you can click Encrypt PDF then download your new file.