Irritatingly, my G1 won't show me PDFs so I've made the Google Docs PDF viewer which will load PDFs on the web up in Google Docs. Google Docs has the useful ability to display PDFs in web browsers without any Adobe software and works (mostly) on Android.
This was very easy to put together as an Android activity. First its necessary to register the application as handling PDFs from the web. This is done via the intent-filter declaration in the manifest:
The action part says my activity will view PDFs, the data part says it accepts data with the PDF mime-type and with a URL that has an HTTP scheme. The browsable category is necessary to allow links from a browser to open this activity.
data android:scheme="http" android:mimeType="application/pdf"/
Second, the activity opens up the browser to Google Docs pointing to the PDF.
This is very simple code to invoke a new intent browsing to a newly constructed URL for the PDF in Google Docs. That was easy.
Intent intent = new Intent();