The AZW file type was developed by Amazon for use with their range of Kindle eBook readers. The proprietary format is used for eBooks that require DRM protection. The file format is the same as the MOBI file type which is used for eBooks that do not require DRM protection.
The AZW format is extremely similar to the MOBI format but boasts superior compression rates and also includes Amazon's own DRM. The DRM works by restricting usage of the file to the device id which is linked to the user details of the owner. A disadvantage of the format is that it does not allow for series related metadata to be added to the file.
PDF is a file format developed by Adobe Systems for representing documents in a manner that is separate from the original operating system, application or hardware from where it was originally created. A PDF file can be any length, contain any number of fonts and images and is designed to enable the creation and transfer of printer-ready output.
Each PDF file encapsulates a complete description of a 2D document (and, with the advent of Acrobat 3D, embedded 3D documents) that includes the text, fonts, images and 2D vector graphics that compose the document. They do not encode information that is specific to the application software, hardware, or operating system used to create or view the document.