Google has just announced the release of Google Docs Android.
You can now use gDocs on your smartphone to view PDF, word docs, spreedsheets, etc, much like you can with the browser version. But with the Android app you can also take a picture of a document with the camera and then use the app to convert the picture to text. The app will also open attachments from gMail.
This app has one other thing the other apps don’t; it’s tied into the Google cloud. That should make it easier to get docs off and on your phone.