You'll need the Adobe Reader (which hasn't been updated in a while).
Handyscan is a MUST HAVE if you want to create PDFs on your WP. I use it to scan receipts for expense reports and e-mail them to myself.
PDFy Pro will allow you to make PDFs of any web pages you come across, which can be useful for sharing across devices.
I still haven't figured out how to create PDFs from Mobile Office documents, but I tend to go to my PC for that today. Hopefully WP8 will handle that better...
My HTC Arrive will not open many pdf files.
When I tap to open the screen goes dark then right back to the email message. If I try to open to many times the phone restarts.
In web pages with a pdf file some open but many will not. when I tap on file it flashes screen then back to web page. The pdf files never show up in adobe either.
My arrive is up to date with software 7.5 os version 7.10.7720.68