The reason why most users choose PDF format to share and transfer documents is because they can be protected by the creator. Content, such as text and images, can not be copied or stolen from such PDF documents.
However if you want to unlock a PDF file without installing any software, I would recommend PDF Cracker. It is a Free online PDF Unlock utility.
It works simply by uploading a protected PDF file through your PC and once uploaded, it will open an unlocked and non-restricted version of the same PDF document in a new window.