Per suggestion above, I checked out OnSet's METAmessage app for PDF and TIF viewing. I signed up for a 30 day free trial of METAmessage using the offercode "4546" that one of my collegues sent me. This is great! Try it out!! I am using a 7280, my collegues are using it on the 7100t, 7250 and 7520.
META has new features that are included with the software, this is what their site says (http://www.metamessage.com):
-Spell-check outgoing email messages;
-Print messages, attachments, and Web pages using any fax machine;
-Set Message Alerts for custom notifications of important messages;
-Listen to Nextel NextMail™ and other voicemail attachments (.mp3, .wav, .lvp);
-Ask Concierge Services virtually any question you may have
-Read attachments with original formatting intact; and,
-Get quick info* such as driving directions, flight information, stocks, weather, and more...
I hear they have an OTA install for 4.0 devices, but I have not tried it.