Strange that Highlighter (and Comments icon) works for some but not all PDF documents. I want it for several long papers that were perhaps converted to PDFs by an association before disseminating to me and others. Can I somehow get the yellow highlighter to work?
Are the other commenting tools enabled? If not then the file is probably secured in such a way that adding comments is not allowed.
If you mean all the Commenting tools on the bar after clicking Comments in the right column (e.g., bold, italics, strikethrough, etc), then the answer is No, those too are disabled. Then I guess I'm just out of luck for highlighting these documents. Thanks a lot, for the right answer, if not what I hoped for ;-) .