I had not yet heard of any app that makes an iPad work like a virtual network-accessible printer 3 but looking now in the App Store reveals at least one 'ACTPrinter' which (with the help of specialpanion software on the source Mac or PC) can print to iPhones and iPads. (I wouldn't be surprised to see other apps that manage to simulate a network printer using preexisting printer drivers.) While that idea is interesting if the end goal is simply to have a viewable version of a document on the iPad there may be equally convenient ways to achieve that goal 3 such as mailing the document to an email account checked on the iPad or syncing the document via something like Dropbox. (If in a format not natively viewable on the iPad you might use print-to-PDF or save-to-PDF functionality first.)