i cant seem to figure this one out.
if i: save the text of said pdf as a file i CAN comment on, and then resave it as a PDF, does it keep my comments from word/office libre?
It always fucks up the formatting when I try it, so it turns into a mess of lost paragraph breaks. That might be because my computer is ancient. If you have the newest Adobe Reader, you can make "post-it notes" and highlight directly on the PDF, though.
I've never come across a PDF where comments weren't enabled. I think the default setting is allowed -- is it possible you have it turned off in your own reader? I can't think of anything else.
Reader 9 is not current, so you might want to try updating that.
As for commenting, it is generally pretty simple. All you should have to do is open the document and click the sticky notes tool, then click where you want to leave a comment. I've attached a file showing this.
Once you're done, make sure to do a save as and then give it a new filename.
If you're having issues creating PDF files from any program like Word, OO.o, etc try using BullZip which is a free PDF printer, it works well in my experience.
If you're trying to comment on someone else's document, you can go to File > Properties > Security to check the permissions you should have as seen below.