It's a little late, since you accepted an answer last year ;-), but, I have always been a fan of FoxIt Pro.
From my answer to Linux PDF reader that shows annotations:
FoxIt PDF reader has a Linux version and say that it can
read, create, sign, and annotate (comment on) PDF documents and fill
out PDF forms.
It would seem to follow logically that any program which can create annotations can also sign them.
Alas, I have no current access to a Linux box, but if you follow my logic, then give it a try.
See specifically http://www.foxitsoftware.com/Secure_PDF_Reader/collaborate-share.php
Provide feedback to documents through annotation and text markup
As an addition to the above answer, to address your question about highlighting, the Technical FAQ says
Foxit Reader is a small PDF reader for you to view, search and print
PDFs. With this software, you are able to measure distances, insert
images, add links, create annotations on PDFs, highlight PDF text,
email PDFs, etc.
This answer probably comes far too late for @Fischer, the OP, but it might help others who read this question in future.