How can I synchronize files of different ibaPDAs that have been recorded almost simultaneously?

You need a so called reference signal that both recordings have in common.
Open both files "not coherently" and display the reference signal of both files.
If the signal is time delayed mark the second file in the signal tree and in the context menu select "Time shift data file…". Now you can shift the x-axis of the second file with a positive or negative offset to the left or to the right until the reference signals are overlapping.

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