I would upgrade to whatever the latest version is.
My I-touch is less than than a week old, is running 2.2.1, and I have not any problems with any apps I have downloaded. Here is a list of what I have so far - mixture of free and pay.
Memory Stick ( pdf and file viewer )
Kobata
Kanjipop
Japanese Audio Flash cards
Japanese Words and Phrases
HumanJapanese Lite
KanaQuiz
The app you need to view Pdfs is called "Memory Stick" ( see my prior post )
Note - You will need a wireless internet connection on your PC, or wherever your pdfs are stored, to use it. Read the user comments before you buy it.
Two other very good apps for Japanese study I can also recommend are: