I am in need of a PDF annotation app. Majority of the times, I will be just using highlight function. I am looking at GoodReader, iAnnotatePDF and PDF Pen. I have looked at Good Reader on colleague's iPad (but haven't played extensively). I have used iAnnotatePDF on my android tablet and happy with its offering. PDF Pen, I have not tried but looks like good option, expensive.. Primary selection criteria for these apps is, the app should be able to open pdfs from Dropbox and save them right where it was, i.e. just annotate the pdf and overwrite the current copy with annotated one (instead of importing it in the program and keeping the annotated copy there). I am not too sure which of these apps can do this job. iAnnotate PDF works like this on android but I don't know if it does on iOS too. I don't know anything about the other two. I will be glad if any user of these programs can tell me if any of these programs perform as I want them to perform. Many thanks in advance.