I just recently got an iPad and have a bunch of PDF's in iBooks which were transferred over from my iPhone. Now I'd like to start using an app to mark up some of them but it seems like the files then want to "live" in that app as well as iBooks. This seems like it will eat up space fast as some of my PDF's are 3000+ pages long. So far I've tried out Evernote, PDF Expert and just downloaded DocAS. Am I right that these apps create a new file, or is there a way to have them use the default iBooks library rather than make a copy? Thanks for any input.