Analog seismic data have been recorded by numerous pen and paper drum-type seismographs throughout the world over the past 100 years or so. Digitizing these data is necessary for studying historical earthquakes and for studying the characteristics of extreme storms and their occurrence in climate change analyses. SeisDig is an interactive Matlab based digitizing tool, designed to digitize entire scanned seismogram “tif” images with a minimum of user interaction. This User’s Manual describes the SeisDig graphical user interface and its use. The SeisDig software is available for download at http://iod.ucsd.edu/SeisDig/. Use of this software is subject to certain copyright restrictions.