As a matter of fact, Goodreader for ipad is the best annotate pdf app out there.
it has a useful feature to extract all text highlited both with goodreader, with adobe acrobat, even with the galaxy note only worthy program for pdf editing: ezPDF.
even adobe acrobat can't extract highlighted text content (if it's not highlited in adobe).
basically, i am saying that iAnnotate functions are all there with ezPDF for android. i've tried also repligo reader but pen interaction is bad and everytime you lift the pen while ending the highlight, the text is deselected again.
what i am doing now is using dropbox to get the pdf, annotate and stickynote with ezPDF, then saving back to dropbox, edit them if necessary with adobe reader, then when all editing is done, i use GoodReader to extract just the annotation and sending them via eMail back to me.