I use Newsstand to view/read some digital magazine subscriptions on my iPad. I'd like to keep both current and older issues of the magazines for future reading and reference. In order to do this I'd like to have each magazine issue backed up and stored in Dropbox or some other online cloud storage website, primarily due to the large amount of free storage space over that of iCloud. This would free up quite a bit of space on my iPad over time.
As an example, here would be something I'd like to do with my digital Wired magazines which reside on my iPad:
December 2012 -> Dropbox
January 2013 -> Dropbox
February 2013 -> Dropbox
March 2013 -> Dropbox
April 2013 -> Dropbox
May 2013 -> Dropbox
June 2013 - keep local on my iPad for now
How do I do this? I looked around on the web and couldn't find a straightforward and consistent way of doing this.
I'd greatly appreciate your help. Please post your comments.
*I have a Windows 7 PC and an iPad 3.