Annotating PDFs
One of the most useful things for me in zotero is the ability to highlight text in snapshots of web pages. It would be tremendously useful to be able to do the same thing in pdfs which are open in Firefox. I guess pdf is some kind of image and not text, but would it still be possible to mark the image/text in some way?
Short answer is no, but obviously annotations you make in your pdf files with your pdf reader (e.g. acrobat professional or foxit) will work for files stored with Zotero.
and you get links to
among other things this: http://forums.zotero.org/discussion/3725/pdf-annotaton-solution/
which in turn has a bunch of other links to relevant threads.
also, you can configure Zotero/Firefox to open pdfs right in skim (or any other pdf viewer) you do not need to import and export pdfs - you just open them, annotate them, save them to the same location (and with the same filename!) and you have yourself an annotated file in Zotero.
If you don't want to configure FF/Zotero to open pdfs in skim by default, you can also select the pdf attachment, chose the "show file" option and open the file from the folder that opens using whichever program you desire.
EDIT: In order to this all inside Firefox you would have to find a program that has a FF plugin _and_ annotation features - there aren't many of those and they are different for any platform.
http://forums.zotero.org/discussion/987/can-i-annotate-my-pdf-snapshots/
This is not currently possible using the zotero annotation toolbar (and judging by the thread above it is such a large and difficult undertaking that it probably won't be possible until a. an open source pdf annotator comes along which zotero can incorporate or b. Firefox gets native PDF support).
However there are several third party pdf annotators around, the one I use is PDF X-change viewer (thread on this below), which has a very usable free version, including a Firefox plugin (if all you want to do is read and annotate PDFs the free version is almost as good as the pro).
http://forums.zotero.org/discussion/3725/pdf-annotaton-solution/
[Edit: oops. Sorry Dan, didn't remember I had already asked this rather than just thought it]