In my iPad app, I have a button that opens a document using a WebViewController to view the file.
For certain PDF documents that were viewable in iOS4, opening them on i
To my knowledge the only way to do this would be if the Adobe Reader had a custom URL Scheme. You could 'intercept' the URL with a PDF extension and re-craft the URL to use the URL Scheme. However, to my knowledge Adobe Reader doesn't provide this URL scheme.
That being said, you can give the user the option to open files with a viewer of their choice (if they save it locally). If Adobe Reader is registered to open PDF files (and I'm sure it is) then you can create an 'Open With' button to determine how it should be opened. It will show all programs that can open a PDF file. For more information on this, check the Apple documentation:
http://developer.apple.com/library/ios/#documentation/FileManagement/Conceptual/DocumentInteraction_TopicsForIOS/Articles/RegisteringtheFileTypesYourAppSupports.html#//apple_ref/doc/uid/TP40010411-SW1