aPhoto is an easy-to-use watermark sign tool.

Install

    No need to install, just decompress your downloaded package.
    If what you used is Ubuntu and its version is Saucy (13.10), Raring (13.04), Quantal (12.10) or Precise (12.04),
You can search and install aPhoto in USC(Ubuntu Software Center).
Or you can install it at command line:  

sudo apt-get update
sudo apt-get install aphoto