Several online tools make it easy to password protect PDF files. I tried password protecting a PDF using this tool https://pdfguru.com/password-protect-pdf . You just need to upload the file, set a password and voila - your PDF is now safe. But I also found that in addition to password protection, it offers some cool features like merging and splitting PDFs, which has been a game-changer for me. The interface is intuitive and the whole process is surprisingly fast. It is user-friendly and the best part is that there is no need to download any software.