If you use Ubuntu, you may have faced the frustration of trying to find a native way to annotate your PDF files, like say, any of the MakeUseOf PDF manuals you know you can download for free. Unless you run some Windows program via Wine, wait for Evince’s annotation features, or learn to use the incredibly user-unfriendly PDFEdit , you’re pretty much out of luck. That’s when you can be thankful that there are developers focused on making web-based PDF tools. There are plenty of PDF tools, many that are document-viewing sites , such as Scribd, Issuu, DocStoc , etc. that beautifully display PDF files neatly on your browser, but not many of these let you do much other than admire the document. Few web-based PDF tools actually offer annotation features, like the ones you can find in Foxit (whose Linux version doesn’t actually have annotation tools) or PDF-XChange , my favorite reader with customizable keyboard shortcuts. Perhaps, you occasionally use PDF files or maybe have a P