There is no such PDF version of documentation available. As mentioned by Joerg, we can download any website for offline reading by many available tools.
But I would recommend you not to do so:
1. AEM documentation is very big in size to save offline
2. Every day it updates
But if you still want to do so, you can use acrobat Converting web pages to PDF, Adobe Acrobat
~kautuk
Kautuk Sahni