To use the "Open In" function - have the book open in Dropbox. Then, there is a download arrow in the upper right of the screen. Press that and you will get the option to open the book in the app of your choice (as long as it reads that format and is installed on your iPad).
Oh, and this works even if Dropbox can't display the book. For example, Dropbox will tell you it is "unable to view [an epub] file." Just press the download button and it will still work to download to your app
Marilyn
|