Portable Document Format Security

PDF is the most popular format for downloading reports, ebooks and other document files on the Internet. One of the niceties of the filetype are the fine-grained security options it lets you set for your documents. In this post you’ll find an overview of these features.

What does security mean here? Generally there are three types of document security (at least as far as PDFs are concerned) – authenticity verification, access control and copying permissions. Lets look at all three in turn.

First, PDF supports digital signatures that let you ensure that the document was created by who you think it was. This is immensely useful when dealing with official reports and secure correspondence. The signature doesn’t forbid the viewers ability to interact with the document – it only lets them ensure they’ve got the real thing. However, this type of security is rarely used by the average user.

Access control means specifying who is allowed to view the document, how many times a .pdf can be opened, and so on. This feature can be very restrictive – for example, a document that is protected by a password can’t be easily converted from PDF to Word. For access control, there are passwords and certificates. A password can either be used to restrict editing, or both editing and viewing. Certificates serve the same ends, but instead of a password that must be remembered there is a certificate file that the user employs for authorization.

The third and final type of PDF security features is copying permissions. These determine which parts, if any, you can print, copy or extract from the PDF. For example, you could create a document that can be viewed by anyone (no password), but that is protected from plagiarists and thieves by a setting that makes it impossible to extract text and images. However, note that a decent PDF to Word online converter may be able to copy the document anyway. The protection is somewhat illusory in any case because anything that can be seen on the screen can (by design) be “copied” with a simple screenshot and some OCR tools.

Overall PDF is a very secure document format, but be careful about what security features you pick for your files – some protection types may be an overkill and inconvevience to the end user, while other’s may offer only an illusion of safety.