The phone allows you to OPEN (not edit) all of these file formats natively.
Editing them you could get Documents to Go, but just for reading you do not NEED an application.
I get a weekly PDF in my email. It will not allow me to open the attachment. I installed Beamreader, and it will view the file, search for key words and all that, but only if I manually put the file on the SD card from my computer. I still can't open it as an attachment and I don;t see an option to save it to the card from the email either.