Add support for PDFs.

[dstein64]

Highlighting is only currently supported on web pages. It would be nice if PDFs loaded in the browser could also be highlighted.

[mvresh]

I was looking for a tool that does this(highlighting text in PDFs) when I came across the extension. I haven't looked into the source code of the extension but I'm interested in working on PDF highlighting.

[hmijail]

I'd love love love love this. I'd sponsor the feature.