It is common knowledge that PDF documents can be protected using the in-built PDF secure restrictions that can prevent anyone from taking certain actions on your PDF files such a printing, copying text or images, extracting pages and so on. But even with the full range of these restrictions set up to their maximum level, anyone can read the contents of your PDF document.
If you want to ensure that the PDF document that you are sending to someone can be viewed only and only by the intended recipient then you can use the free Secret PDF software. As the name of this software implies, Secret PDF keeps your PDF documents secret and makes them accessible only to people who hold a secret passkey to unlock the PDF files.
When you launch Secret PDF, you will be show a number of options that you can choose from – Encrypt PDF, Open PDF and Get Local Key. If you want to encrypt a PDF document, then you should choose the last option – Get Local Key to generate a really long encryption key. You should store this key somewhere and then choose the first option – Encrypt PDF, choose a PDF file, enter the encryption key and save the encrypted PDF file along with a new key in a text file. This new key should be given to anyone you want to be able to open the encrypted PDF file.
Anybody who receives the encrypted PDF file along with the decryption key, should be able to open this PDF file using Secret PDF software. This PDF cannot be opened using any other PDF viewer. You simply have to click on the Open PDF, select the encrypted PDF file, supply the key and it will be opened.
One of the drawbacks of Secret PDF is that it makes everyone dependent on Secret PDF. You cannot open the PDF files generated by Secret PDF in any other software. Other than this, Secret PDF seems to be doing a great job at preventing unauthorized access to your private PDF files.
You can download Secret PDF software from http://secretpdf.org/.