Go to App
This is been my go to app for PDF since my first iPad.
Im currently on my third iPad and by third phone. This is always the first app I download. It allows me to sync with other servers and I have all my information including my work schedule available to meet on all my devices.
While it is not as fancy looking as some of the other apps it is is functional and also for half the price of many of these other apps.
All in all one my favorite apps and I highly recommend it.
Doctoall about
GoodReader PDF Editor & Viewer