If your 'scope has an RS232 port then use an ordinary terminal program on a PC
to capture the datastream to a file that you can later manipulate. It may be
possible to send in any of several formats, but as you mention a plotter it is
likely to be HPGL data format.

If it is sending HPGL then it is all printable ASCII characters and there are
programs on the web to convert HPGL to printable formats. You may even be able
to find a graphics package that will load an HPGL file to convert to some other
format more useful for what you may want to do.

If your scope has a GPIB port then this will be a faster method of downloading
the image than the serial port. NOTE that GPIB is a parallel interface method
for controlling instruments and has no particular relation to how the
information is printed or plotted from the scope screen. It may be that the
scope can print to a GPIB printer or plotter without a GPIB controller, but this
is independent of the data format for the screen image.

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